Not true.
I play CS source a lot of the time with no probs at all.
Haven't come across a game it won't play yet.
This doesn't mean that I like the motherboard, I don't. It is a pig to set up and in my opinion has been released WAY too early. ASUS have a lot of issues to "iron-out" with this mobo.
Power is its biggest problem. Ignore what ASUS recommend, it needs more power. I have a 400w PSU with 17A on the 12v rail and I can only just run it with one of my 6600GT card,, 1 x HD and 1 x DVD writer. Put the second graphics card in and nothing happens.
Have just ordered a Tagan 480 PSU at another £70 on top of the £520 I have already spent. I'm not a happy bunny!!!