Biggest issue (for me at least) is 3D graphics performance, or rather lack thereof.
My laptop dual-boots - I use Windows for gaming and Linux (Mint currently) for almost everything else.
Any games I can (Dwarf Fortress, etc) I run in Linux, but there are many games that either just flat-out cannot run or run too sluggishly to be playable.
Have to agree here at the moment, though I blame GPU makers. Ati's Linux drivers are problematic (open source Radeon is great but lacks performance wise).
I'd have to agree, I can run most of the source engine games at max quality 60fps on my laptop running Windows. When I switch to my linux install on the same box it's much slower and a much less polished experience.
On even my old machine I tried running UT 2004 on Windows then natively on Linux then on Wine on Linux and Linux beat the performance on Windows hands down.
I'm not the only one, when Valve ported their engine to Linux the performance was higher, I believe I read recently it's still higher than on Windows.
edit: I use nVidia graphics cards and the restricted drivers in the Ubuntu repository, old machine and my new one.
My laptop dual-boots - I use Windows for gaming and Linux (Mint currently) for almost everything else.
Any games I can (Dwarf Fortress, etc) I run in Linux, but there are many games that either just flat-out cannot run or run too sluggishly to be playable.