Sadly, for those people building their own computers, driver problems are going to be even worse... I have never been able to get my ATI/AMD graphic cards to work properly under Linux...
I know that one might say but majority of users do not know this, but from what I can tell from participating in gaming communities, these guy do proper research before buying a new rig. I can totally see lot of people who solely play Valve games (TF2, L4D, Dota2, CS:Go, CS) will try Linux if their games work on Linux.