New on Linux... huumm, sounds creepy..
1st: Ubuntu is great, mainly about all updates are eazily done.. apt-get update ... than apt-get upgrade ... you will always be "ok"...
2nd: Ubuntu come with some newby gaes, after that you will find Doom 2 as great add on..
After that, you will be really doomed, because needs to go out and earch for open gl games, there´s a lot, but you need to search.
I always used lunux as development station, no hardcore gamming.. so.. if you wanna go to hardcore gamming, try a dualboot with xp... :)
PSN: franco-br
MGS4, GH, MW2, GT5p, WipeoutHD, etc..etc..