It boils down to being a 2.5ghz x2. Performance is pretty much what you'd expect. You will probably bottleneck a high end GPU but not by a massive amount. I'm one of those people using it with just the 780G IGP so I can't provide benchmarks for you. But I've had plenty of time to gauge the...
I have two s939 machines still in operation. Opteron 180 and 144. Been reliable workhorses for me and should continue to serve their roles well for a couple more years, really.
I have that Biostar board and it's great. I'm not overclocking though so I can't comment on OCability. I have it running an AMD 4850e low power CPU and 4GB of ram. It's a fantastic setup for my light office work.
AMD still offers a compelling choice for people who aren't necessarily looking to dominate in Crysis.
Take a peek at system #2 in my sig. It's a great office machine that I built for $220 including a slim case and PSU (had a spare HD and Vista license). System uses very little power, flies...