AMD APU performance on Ubuntu?

Hi guys, so I'm building a budget gaming PC with the APU, but being a cheap bastard I don't wanna get Windows, I'm thinking of Ubuntu.

With Steam running on Ubuntu I think it will be perfect. However I only heard of good driver support from Nvidia but never AMD, so does anyone have experience gaming with Linux and an AMD card? If so, how does it performs and does Nvidia has a better advantage? I'm also wondering when the non-source engine games will start running on Linux. Thanks guys!

I do game on Ubuntu and I run AMD graphics but my current rig is at the other end of the scale... General rule of thumb nivida is a better bet. Intel is very well supported but to get half decent onboard Intel graphics the CPU will blow your budget.
AMD is a good choice, try to grab one of the quick quad core Phenom II. 4GB of RAM will be more than enough. Almost any gaming card from nvidia, even an old one but I wouldn't go much older than an 8800 512MB. Anyhow there are plenty of guys here that can help with spec~ing a cheap rig.

On the Ubuntu side of things install the 32bit version, Ubuntu will automatically install with the PAE kernel. The 32bit version tends to run a little better than the 64bit with fewer compatibility issues. Unless you know you need 64bit or you have loads of RAM 32bit Ubuntu is the way to go.

I've beent using Ubuntu 64bit since Ubuntu 9 was released. Never had any compability problems.

Same, only compatibility issue was the R.A.T.7 but I just wrote a small patch for it and it works perfectly. 

AMD drivers are shit you will have issues.

I'm running an A10-5800K on Debian. The non-free drivers were a bit of a hassle, but I got them installed and the APU works perfectly for my needs, which would be running Quake Live with max graphics at 1920x1200.

I don't remember how but there was a write up about 2 or 3 years ago where I got 16GB of ram running on my 32bit Ubuntu Desktop.