And here are some performance numbers, openarena, Very High Quality, 1024x768:
no MSAA: 74.6 fps
MSAA 2x: 61.1 fps
MSAA 4x: 41.6 fps
MSAA 6x: 29.7 fps
Wow, that's pretty good.. It's already pretty close to what you would expect from MSAA on DirectX & Windows. As a Windows gamer, nobody typically runs MSAA higher than 4X because it tends to be rather inefficient.. It's better to go for 8xCSAA or AdaptiveAA to get better than MSAA 4x because you don't get that nosedive in performance with CSAA as you do with MSAA. Yet the end result of 8xCSAA is still better than 4x MSAA... Of course, it's even *better* to just buy a higher resolution screen to begin with, but for laptop users, that's not an option.
At least those people with low end r300 cards and a low resolution laptop screen now have their 2xMSAA... That is definitely a nice Christmas gift!