Won't really know for another month or two, when the Dell equivalents ship, and benchmarks from others-than-Apple become available.
Of course, then the next question that will be asked is how easy can the CPUs be replaced on the dual CPU configuration...there will invariably be those who will want to buy the 2.27GHz with the intention of upgunning the chips once they drop in price...IIRC, that's how the first dual-quads got made.
-hh
Only thing is, I don't believe that you can replace 3500s with 5500s.