I'm looking in to gaming on Ubuntu (using PlayOnLinux - i.e. wine). What is the most modern game you have run at an acceptable framerate and what hardware were you running? Did you have to tweak your wine or gfx card settings? If so, how?
Before everybody lists out every single game they've played on Ubuntu through Wine, check appdb for specific games you want to run on Wine. Some work at near-native speeds, some don't work at all.
However, the "most modern" games I own are Modern Warfare 2, Dragon Age: Origins and Fallout 3. All work fine on my i7 920 + Nvidia GTX260 but then again, I didn't buy them until I knew they would. In a perfect world, MW2 could run a little faster.
Dragon Age and Fallout both took a lot of wine-hacking to get working originally - They're somewhat easier now but I still patch in WinePulse to simplify audio problems.
For Source games (that is Valve, not the open- variety) like HL2, Left 4 Dead, TF2, etc, you'll find that things run pretty well.
For me, it was MLB 2k9 which amazingly runs pretty much flawlessly in Wine. The frame rates are around 20-30% slower than Windows - but still acceptable.
The cool thing was that it ran in Wine unmodified. (No tweaks or fiddling around.)
Disclaimer: I didn't test installing it. It was already installed when I tried running it in Wine.
Heros of Newerth (HoN) - a team strategy game like Dota (WC3)
It has a native linux version and installer.
Great graphics and is very addicting.
You can play it with your "windows friends" too ;-)