The End of The Beginning
Not counting 3.0 and 3.5, I've run a campaign using the Pathfinder Beta rules (my Rise of the Runelords game that never survived out of the Skinsaw Murders) and my Pathfinder RPG game (Council of Thieves, up to 9th level characters and through the Infernal Syndrome). I've also played up to 7th level in the Legacy of Fire AP, 4th level in a Pathfinder version of the Shackled City AP, and 5th level or so with a character in Pathfinder Society. I also have run a few Pathfinder Society games under Pathfinder RPG as well.
So, on one hand, I've played a good amount of Pathfinder. One thing you might notice, however, is that the highest number in that whole bunch is 9th level. I think that is kind of telling. It's hard to put your finger on exactly when it happens, but I do think at some point you loose the wonder of "one more encounter" so that you can level and do something new and cool, and where you start to realize you HAVE to do X, Y, and Z or the system will kick your ass, or the GM is going to be doing a lot of tap dancing around the expected flow of the game.
Been Here Before?
Before I delve too much further into this, I wanted to look at some of the 3.0/3.5 games and see where I ended up. I had a game that died at 5th level, and ones that reached 7th level, and 13th level. I also played in games that got up to 4th level or so and up around 7th level, as well as a bunch of one shot adventures at various levels, usually around 5th to 9th level.
First, to describe the 13th level game. That was a game with a group of people playing at a private venue, with me having a metric ton of house rules. I don't like being that guy, but the higher the level the campaign rose, the more I felt I had to put some damage control out before a train wreck could happen, so my list of house rules got longer and longer. No one objected, but I didn't like it. It wasn't that I thought my house rules were unfair, and I tried to make sure everyone knew about them and had a copy before I implemented them.
Part of what contributed to not wanting to be the house rules guy had to do with reading message board posts. I read one particular contributor to a site that made a really compelling argument that when people sign on to play a game, and they aren't your buddy, and you don't know them all that well, what is bringing them to the table is the game itself, and the further you deviate from that, the more you are asking them to trust you as a GM, when they may not have much experience to base that trust upon.
This became even more important to me when I started running games at the FLGS, and especially when I was running Pathfinder Society scenarios.
I mention all of that in order to point out that I don't think that the 13th level game would have reached that level if it weren't a home game where I had a huge stack of house rules going into the game. Too many gonzo spells, prestige classes, magic items, and feats towards the end of 3.5 for me to have juggled it all had I not chopped up and mutilated the options allowed.
Even with all of those house rules in place, we actually had a fight with a band of demons at the high end of the campaign that lasted over half of a marathon 8 hour session. The fight was fun in its own way, but somehow that really didn't seem like the way to go. I don't even run sessions at the FLGS that could have encompassed the timeframe of that fight.
Part of what Pathfinder was suppose to do was to streamline the problems above, and balance the game out a bit better. The problem is, getting up around 7th to 9th level, I'm still seeing the same problems that I saw in 3.5, although I have to admit, some of those problems were exacerbated by the same problem 3.5 had . . . namely, rules supplements.
Before I dive into this section, I'd just like to say that I don't blame any player for taking this option. Honestly, unless a player is being troublesome or trying to pull a fast one on the GM by doing things without explicitly explaining what he is doing, the players operate in the parameters set by the GM, so ultimately, if you allow something as a GM, you've only got yourself to blame for problems that come up.
Disclaimer in place? Good. I hate paladins in Pathfinder. When I first read the description of smite, I thought it was a mistake. The original argument was that paladins, when they smite, would use their smite, and if they missed, it was gone. Why would your god want you to smite something, then let the ability fade just because you swung wide? I get that argument. That is actually an easy fix. Your smite lasts until you actually hit your opponent. Hooray! Game design is fun. Wait . . . what? The fix is that you smite an enemy and from that point on, until it dies, you get your smite for every single attack?
And on top of that, you gain your charisma bonus to your AC as well? And you do double smite damage to undead, dragons and evil outsiders? I can't say that paladins were that bad in 3.5, but I can say that this new rule was very annoying. At low levels, it wasn't too bad, but from mid level on, it became very tiresome. Not only is the paladin likely to dish out some insane extra damage, but he's a fully armored class that gets yet more of a boost to his armor class when doing his job in the party.
It it weren't for the fact that paladins can be a pain to play due to alignment, there would be almost no reason to play any other martial classes. I realize that combat in d20 systems can be swingy anyway, but a crit by a paladin can easily come up often enough that your BBEG never, ever get a chance to shine, especially if they are built more for endurance (hit points) than defense (armor class and movement).
Magic items and wealth continue to be the greatest issue in d20 games that I have played. It's hardwired into the system that you will need boosts to your ability scores, armor class, and ability to harm an enemy that you will not get from leveling up. On the other hand, I've noticed that there are a lot of flaws in the logic of assumed wealth per level.
We'll skip the "PC died and replaced by a new one issue." Pathfinder actually addresses this by noting that you should either bring the new PC in with no wealth or use the wealth of the old PC, rather than stat up the new PC with their own level appropriate gear, to keep from inflating the party. Good move on Paizo's part.
The problem is that any expensive magical gear counts as part of your wealth per level, and some magic items can be wildly effective in some places, and worthless in others. "We can fly" can completely negate an encounter, or it can be a needed ability when dealing with a creature like a dragon that can fly itself, and is constantly out of range of most of the party.
Add to that the weird quirkiness of what harms some higher CR creatures, and you have a mess where PCs always want more because they always feel like, even at the proper wealth level, they are under equipped and need to sell and trade off for the next encounter.
What do I mean by the quirkiness of higher CR creatures? Keep in mind, I'm actually a fan of the "golf bag," i.e. having lots of different weapons that harm different creatures. It's a genre staple for monster hunters to have a whole bunch of specialized gear to deal with different threats. The problem is, Pathfinder (and 3.5 before it) has some wonky requirements. Are devils hurt by silver? Most are, but lots of them also require a holy weapon as well. Can I cleave into a golem with an adamantine weapon? Well, probably, but it should be magical as well. Demons? Cold iron, magic, and holy would help, just to be on the safe side.
The problem is, once the above weapons have to be magical as well as composed of a special material, and holy to boot in some cases, you are talking about a major, major investment in gold if you don't have a campaign "theme" locked in where the PCs aren't likely to meet certain types of monsters. On top of that, once you spend that much on a weapon, why not just save up for a weapon with enough plusses to overcome the whole she-bang? Sure, it kills the flavor you were trying to create, but it makes more sense in the overall game.
"This monster can only be harmed by a blessed, silver, magical weapon, or by what we like to call the magic of greater plusses."
This is another one that you don't really see biting you in the rear until you get up to higher levels. However, once characters can swing multiple times, things do start to slow down. If that were the only issue with action economy, however, dealing with the slowing game wouldn't be so much of a problem.
However, Pathfinder has also introduced new spells and the like that allow for extra actions (Blessing of Fervor) as well as immediate action casting. If only one of these factors were in play, it, again, wouldn't be quite so bad. But when you have one character adding actions to other characters, and another player taking immediate actions, and several characters with multiple attacks, some of which might have been criticals . . . things slow down.
Not to mention the fact that one monster against a group normally has a problem with action economy (i.e. they take one action to the party's four to six or so). When you add extra movements and actions on top of that, you can almost never have one monster as a credible threat to a whole party unless its wildly out of sync with what the party should be facing, or that monster has been heavily tweaked by the GM.
(Note the recurring theme: The system can work, if you have a GM that invests a LOT of time in the system. And I mean a lot.)
Let Me Sum Up
1. Low level is fun for the GM, somewhat fun for the players.
2. Mid-level is pretty fun for the GM and the players.
3. Starting around 7th and building up to about 9th, the game gets to be a pain.
4. Paladins are way overpowered if you use evil creatures as any kind of dramatic encounter.
5. Magic item shopping is built into the game, and has to happen unless you do a lot of work as a GM to work around it, but it grinds the game to a halt and tends to really harm suspension of disbelief.
6. Supplementary material makes all of the above worse and adds in even more trouble, like:
a. Immediate actions on a regular basis
b. Fiddly point based systems that are more trouble then they are worth (Summoners and their Eidolons)
c. Spells and class abilities that allow characters to do things the baseline game doesn't normally assume (door sized walls of force, daily commune spells, pit spells in areas that can't reasonably fit them but should because they are extra dimensional spaces, etc.)
I Want To Be Wrong
I will fully admit, I want to really like Pathfinder. A lot of what drove me over the edge were the options in Ultimate Magic that swung from "useless" to "obviously better than anything in the core." I fully admit that it could be a deficiency in my own GMing style that has failed to overcome some of the above problems.
I really do welcome discussion on this. I don't want to argue, but I am willing to look at other points of view, but I will point out one last thing: I am really looking at this from a "very very minimal house rules" point of view, meaning that most rules have to work on an "on/off" paradigm, not a "use it but use it this way that is slightly different" way of working.