I am running skyrim with a single core (AMD Athlon 64 FX-55) and a Radeon HD 4650 GPU with 3 GB of RAM and I am getting around 30-40 fps with low shadows and high-ultra everything else and 4x AA, though the controls are lagging behind around 5-10 seconds when there is a lot on going on in the screen (2-3 bandits) and load times are a little slow. I have to set skyrim to a high priority every time I start the game as well. I think the game is fine but it is frustrating hitting the attack button and 5 seconds later spraying fire non stop all over the place, wasteing my magicka.
I think it is because the processor cant process my mouse and keyboard input at the same time as Skyrim, but I haven't found anything from a google search on it yet.
Edit: I turned off AA AF, and went in windowed mode and now I have a decent fps AND no delay with my controls, so I am happily playing Skyrim on the PC now!