Heck, late kernel/Xorg support is the least for me. Compared to things slugginess and lag I often have on the desktop(it's MUCH less with radeon). Pretty much everything fullscreen and hardware accelerated is glitched. Right clicking on a fullscreen youtube video temporarily glitches up graphics for a moment and then no right click menu. Sometimes there is, but it's invisible. In fact when running a game or anything that combines fullscreen and hardware acceleration(flash in chrome). I can't see anything else other than the fullscreen thing, no matter what I do, except in between glitchy graphics when I alt-tab, activate a hot corner, etc, It's really annoying .. You can see it happened, but you're still shown the fullscreen window. Sometimes by moving the cursor around I can see the windows in expo mode when it happens due to the corresponding hot corner, and then a glitched texture makes a sort appearance before the fullscreen window is again falsely displayed, since I interact with the expo mode. Same with workspaces hot corner and more. Pressing media keys also glitches the graphics temporarily while the sound icon is displayed when in a game/fullscreen-accelerated-window.
So recently I started using the Gala window manager. Very fast, fluid, smooth. Even the previous bug didn't happen in many cases. BUT screenshots would show some random image of another window not in forefront or just background(some buffer madness must be going on there), transitions when logging in/out seem very glitchy(glitchy textures like usual), games/fullscreen-accelerated-windows present me with a nice purely black screen and similar goodness.
So I found a way to cure these bugs surprisingly! Yeah, you guessed it! "sudo cp /usr/bin/gala /usr/bin/gnome-shell && gnome-shell --replace".(WTH?)
You might say "what?". People more familiar with Catalyst may understand though. Catalyst works very well in general(as described previously ..) so many application specific hacks are used(I could say tweaks, fixes, but hacks is probably more correct). It appears that it severely breaks mutter based window managers, so more hacks were added for that(who would guess?). But Gala (and apparently Cinnamon) are not on the list to get "fixed" and miss on all that goodness resulting to mentioned bugs. But by using an appropriately named executable file I was able to activate them. So here's the thing. While all the bugs that mentioned for Gala were gone now, all the previously mentioned issues suddenly appeared... xD
Now I so hope power management for radeo comes about soon ... :/
I mean seriously .. And it's that way in many different version of many different distributions, but not with radeon(I have other issues there though, mostly my laptop emitting amounts of thermal energy similar to a nuclear reactor when just web browsing etc).
Why don't they fix this kind of stuff? And just apply more application specific hacks that bring other problems? Can't they make a driver work right? UNIVERSALLY! NO APPLICATION SPECIFIC HACKS! It's pretty obvious that the driver behaves very differently for different kinds of apps, like games, window managers and other apps. I understand performance profiles .. But this? I mean application may not work AT ALL without the hacks, while they would under ANY other platform.(by platform I mean other proprietary or open drivers)
I mean, even certain OpenGL commands just fail if not issued in certain ways/order, while they work on the other drivers.
Instead we get new performance profiles and a graphics corruption fix which isn't really a fix since it doesn't solve the issue, but causes another one apparently ..
Thanks AMD! :P
Yeah, I know, they care for "workstations". I don't recall my laptop saying workstation anywhere though, and whatever AMD card I saw/bought seemed to advertise games on it, not render farms or whatever ..

Anyways, hopefully, good times are ahead for the open radeon driver. But for me, it's just not there yet .. :/
Should I add, Elementary OS plans to blacklist fglrx from Jockey .. xD
They're not very wrong I think .. :/

Whoops, wall of text! It's probably due to my love for AMD!
Seriously, I like AMD, but just fix the damn drivers .. -.-