These aren't great, but they're WAY better than they used to be.
Some background. I care about precisely three applications:
* World of Warcraft
That's it. xterm and firefox work everywhere, so the only interesting thing, to me, is WoW performance.
Some years back, I had... Hmm. Probably a Radeon 9600 or so. Maybe a 9800. Anyway, I had that on a Windows box, and I was doing some WoW addon development, and I was really hating the Windows experience -- such as the 5 second lag to resync my monitor when I changed from 1600x1200, 60Hz, to 1600x1200, 60Hz. Whatever.
So I rebooted to Linux, copied some files over, and tried WoW. It ran great... Until I found problems, such as "1 second lag upon changing target" or "1 second lag upon any of a large number of video effects".
After reading reviews, forum posts, and so on, I went out and picked up a GeForce 7950, swapped drivers, and... It was flawless. Worked better, ran faster. Huge upgrade.
Since then, I've gone through about 4 nVidia cards, all of which have been livable. There was one brief period where fog rendering got completely broken, which lasted for about one minor driver update.
Anyway, it's been a while, and I had heard that ATI's drivers were a lot better, so I decided to get a 5750 fanless card (I'm big on fanless cards) and see how it worked.
* The install process is pretty livable. It worked, anyway.
* The driver is not especially stable in the face of the sorts of changes one can make through the UI.
* Especially not in DirectX.
* OpenGL works.
* I don't think this card should be noticably slower than a GeForce 9800GT. But it is.
The most impressive example I got of a Just Plain Crazy failure mode is that enabling full screen glow in DirectX mode causes the entire 3D view to flip upside down. I can't even dignify that with such language as "doesn't make any sense". That's just insane. (Note that the nVidia drivers I used most recently couldn't do full screen glow in directx mode either.)
The card makes a bit of a high-pitched whine; I'm told that's common on new hardware (indeed, that's why I don't have a GeForce 260 right now -- this one isn't nearly as bad).
I've had three or four cases where wine dropped into a debugger upon an attempt to change some UI feature. Ugh.
* Way, WAY better than it was four years ago.
* Could definitely use work, both on stability and performance.
* The hardware price/performance/power requirements look to have improved a lot.
I'm easily annoyed by fan noise and the like, but the big thing to me is that I'm sort of disappointed by the performance. I'd expect a card a full year or so newer to be at least marginally faster, and on paper, the 5750 looks like it should be noticably faster, or at least not particularly slower, than the 9800GT. In practice, it's about 20% slower, maybe a bit more.
Two years ago, I would not have recommended even trying ATI's Linux drivers. Now, well, they're still clearly second-place, but they're a lot closer. The substantial edge in wattage is pretty attractive, too.
I do wonder where all the time is going, though. There is no reason for a modern system to be running <30fps in low-population old-world parts of WoW.