I'm running a Eberron game right now and I'm aiming for the "power level" of the game to go off around 8th level. I'm using plenty of NPC classes for NPCs, action points and a ad hoc repuation system to make the group have a "low-level/high-action" experience. I'm looking forward to having epic adventures after 12th level. I want the world to be their sandbox while avoiding all of the additional muck about the Epic handbook.
This is an impression about the subjectivity of fast advancement. In Eberron, where most NPC's are low level, it's easy to be 12th and have epic adventures...you're more powerful than most of the people in the world.
In FR, for instance, it's harder, because most of the NPC movers and shakers are absurdly high level, to a "they will always be more powerful than you" kind of point. Fast advancement doesn't hurt FR at all.
Me, I play a lot of Planescape. Since the adventures are on the planes, high level is the order of the day, and there are things out there that define power itself. You will never be high enough level in my PS campaign to ever breeze through an encounter I don't want you to breeze through. If you're 40th level UBERGODS, I have a single Balor tucked away in some corner just waiting to take that 3k hp down to the single digits. It doesn't matter if you're level 1 or level 100, I will never run out of challenges for you. That's part of the inherent advantage of PS -- it's so diverse, it's very easy to create any story you want out of it.
I think the reason that threads like this appear is that some GMs running 3.x games suddenly discover that their characters advanced from 1st to 15th level in a couple of months in-game - it's a common enough concern that I've seen it raised on bulletin boards many times over the years. I'm not suggesting that it's a "bad" thing, but it is a recurring point of contention with some GMs, as evidenced by the response in this thread.
I guess I can't easily sympathize with a DM who "suddenly discovers" they have high-level characters on their hands, since XP and pacing are entirely in the hands of the DM (even using the default recommendations). Surprise over the fact that the party wizard can suddenly
teleport when one month ago he couldn't? That doesn't seem to be the system's fault, that seems to be an oopsie on the DM's part (not that we don't all make significant oopsies every week as DMs

). Blaming the D&D XP system for the woes seems...odd, to me, since a DM effectively controls the entire situation herself. But maybe I'm missin' somethin'....
The problem with this approach, for me, is that all it seems to do is reinforce the idea that 3.x instilled that the PCs are the most important entities in a huge dynamic campaign world where there are tons of other things going on - some of which may or may not affect the PCs - either on purpose or at random. My answer to that idea is "Wrong! It is my campaign world, I'll run it how I see fit." If I want to speed up or slow down the progress of level advancement, that is my prerogative as a DM.
What's wrong with the PC's feeling like they're the most important entities in a huge, dynamic campaign world where there are tons of other things going on? Heck, what's wrong with them BEING the most important entities in that world?
You should run your world as you see fit, but D&D *is* engineered to have the PC's be heroes, unique in the world, not just part of a greater whole, but somehow definitive of that whole. Because people like feeling like they had a humungous impact on the campaign world. In the campaigns I run that aren't PS, my players are constantly the "chosen ones" or the "reincarnation of the ancient heroes" or "the only creatures capable of saving the universe." Even in my campaigns that are PS, with the gods and the like, the PC's affect the world on their own level -- they define topography, shift towns, defend family and friends, discover world-shaking things, define reality in their own terms. What's wrong with that? Everyone defines their campaign world as they see fit. The implied D&D world is one where the main characters are several cuts above even the powerful NPC's, eventually....that's wrong?
Basically my case is that this:
Others may feel the same way, but I don't think a group of adventurers should be able to amass a fortune and a lot of power in a few months (i.e. go from level 1 to 9 in 2 months of game time).
Isn't so much a problem with 3e, it's a problem understanding what your players are doing. They didn't go from 1 to 9 in two months because of D&D, they went from 1 to 9 in two months because you made them. Space it out, sprinkle in low-level encounters that give crap for XP, and take it easy. It's not the XP system that's at fault, here. Though you may want to change it to better suit your own ends, it handles slow advancement just fine, I think. Those 13.3 encounters aren't the *only* encounters, they are just the encounters at your EL.