Fairly recently upgraded to an A64 system - currently running it at 2.3Ghz (or 2.4Ghz when it's not too hot) for playing games with full stability.
The increase in speed over my old Athlon XP 2.3Ghz + NF7-s is amazing for UT2004 .. at last I can play @ max details @ 1024x768 without so much of a hit on most maps (9800Pro graphics card).
However, I have found that a few maps tended to suffer from what I would best describe as "texture choking" i.e. where instead of it getting jerky as it does for low frame rates it sort of slows down whilst still being smooth as if you had just hit a more dense atmosphere (or wading through syrup). Most notably maps such as:
Icetomb (I know it's lame)
Inferno
Junkyard (in places)
Well, I have good news for anybody who has this same problem ... whereas on the NF2 aperture size didn't seem to have any noticeably impact on games performance ... on NF3's it does - I set aperture size to 256MB from 128MB and this slow down problem went away