I don't know how many fps I get(is there an option to see it in SupraHLE?). I only know that it's playable(fairly good speed), the sound is a bit skippy in some games sometimes, but nothing to bother about. I suppose it will run great for most pcs, since mine is a PentiumII 400, 64MB, Voodoo2.
truffles: I don't know the fps for Mario Kart, but the speed is great and the sound is quite good. Seems a nearly if not completely perfect emulation.