The concerns about the monk have already been stated in depth - inability to keep up with to-hit/AC curve, even against mage targets, at higher level; lack of tools for mobility in later levels, outmoding of most class abilities in upper-level play, general lack of damage, multiple ability disorder in a big way.
The fixes given in Pathfinder give him a little larger toolbox, but unfortunately, the toolbox wasn't the problem.
To answer your posit, Jason, the rogue gets by because he has the clearly pre-defined role and a need for only one prime stat. His sneak attack and trapfinding abilities remain useful at all levels, and his talents are actually pretty good. When I play a rogue, I know what to do. When I play a monk, I start out having an idea of what to do, but it becomes much more unclear in later levels.
One of the likeable things about the Game That Shall Not Be Named is the motion towards starting with the -job-, rather than the class. In that vein, here's a hastily thrown-together idea for your consideration:
The Monk As... Shock Defender
This is an interesting role possibility for the monk. It basically means the guy who gets into the mix to start out with and starts setting up the battlefield, starts getting the opponents on the defensive. He can't stand in there forever - like a fighter can - but he's got just enough tricks to live long enough and distract the mages/artillery/fatties while the fighters clink forward and the rogues skulk up.
He's already partially well-suited to this, with a handful of immunities, SR and great saves. His HP is actually OK for this role... it's his Achilles' heel that keeps him from being the permanent defender. He's just the setup guy. But what keeps him from being able to do this is his AC. It's just too low.
So for changes, let's start out with a doozy. What if... we gave monks leather armor proficiency, and redid their abilities where they played nice with it? And... revise flurry of blows to say that in rounds we don't use it, we get a shield bonus starting at +1 at 1st, moving up to +2 at 6, +3 at 12, +4 at 18.
I'd also recommend that Dodge come as a totally free bonus feat, perhaps to replace Still Mind at 3rd, though this isn't totally necessary.
Suddenly, our monks' AC potential rises by seven or eight. Fair enough that most of us were playing with mage armor before anyhow, but now we can get a couple of points on top of that. Taking a reasonably geared 10th level monk, we're now looking at a much-more bearable mid- to high- 20s AC. Not in the 30s like a fighter, but at least iteratives are missing us on occasion now.
We'll need to reframe a couple of the monks' other abilities, such as revising abundant step to where we can use it before an attack (perhaps, in a psionics-like vein, keep it as-is but let that occur for an extra point of ki?) I'd also like to see wholeness of body be able to be a swift action, and add Wind Stance (cool feat, btw) to the bonus feat list. Two more things to polish off the monk:
At 14th level, let's add "Diamond Touch." Very simple - any opponent who is in a grapple with the monk is considered to be under the effect of dimensional lock. At 16th, let's add "Diamond Fist." On any successful hit by the monk, any freedom of movement or similar effect is suppressed until the end of the monk's next turn.
Take away quivering palm, we don't really need it.
The end result is a monk with more respectable - but not great - AC who can get into the middle of a battle quickly and start controlling the actions of his/her enemies. As mages and clerics get wilier with their teleportation tricks, the monk really shines as he becomes their nemesis if they try to get away.
The monk still has to be very careful... he doesn't have a wealth of hitpoints, especially because of his MAD and the fact that his con-boosting slot is probably taken up by his amulet of mighty fists. But along with the new combat maneuvers provided, the monk now becomes a strong melee hybrid defender/controller, and has a truly unique role in the D&D hierarchy.
