I literally just built myself a new computer a few days ago with an AMD cpu and an ATI videocard (because I suddenly realized I could afford it and still have enough money left over to move when I'm healthy enough to do so), so, uh, yyyyyyeah. Everything's fine so far, though this thread is making me slightly nervous. It's my first AMD CPU but I've had some ATI cards in the past and they performed as well and for about as long as the nvidia ones I've had.
Actually, there is one little thing that's not fine. My SF4 arcade stick doesn't work on account of it expecting some bullshit Intel proprietary USB protocol on the motherboard and I'll need to get a PCI USB card if I want to use it. So that sucks pretty bad, but for a first build, if that's the worst thing that goes wrong then I'm not gonna complain too loud.