I'm running a P4 with a 9800, and I can run this game. Not well, as my CPU is really bottlenecked, but it runs. I think I'm something like 164th on the beta ladder, but the ladder still isn't used when matching players. Often you'll fight people who clearly don't know what they're doing, and are quite surprised when you descend on their base with 50 bots while they still only have a single factory and a couple pgens.
For a couple weeks there the tech1 bots were majorly imba. They were accurate while moving, and could dodge pretty much anything just by you microing your forces. GPG cut their health in half, and now it's all good again.
If you're buying a rig for this game (as I am) get a good CPU. DX10 is great and all, but CPU is much more important in this game. When you have 200 units blasting away at each other, and another 200 on the way, things can get a little choppy without that second core. I'll buy it, but I don't think I will truly be able to play it to it's fullest until I'm running a beefier rig.