I have been running both Windows 2000 and Windows XP on my home PC and work PC since they were released and I had not noticed much if any performance differences. A close reading of the IDG report told me why. IDG found that both XP and W2K performed well on SMP boxes. Both my home and work PCs are dual processor boxes. Very valuable for certain types of penetration testing such as password cracking.
I am not a game player. I wonder what the implications are for XP Home? Although the IDG tests don't cover game playing performance, I suspect that it will be a problem for game players expecting maximum performance from their systems.