SP2 no problems here.
EDIT:
Out of 7 computers i fitted SP2 too, i have suffered only one with problems.
This one was randomly rebooting when clicking on links or windows close buttons etc.
Tracked this down to an old graphics driver installed, ATI Catalyst 3.2 i think.
With SP2 microsoft decided to dictate and basically control which areas of memory they want graphics cards to have access to.
The idea is to make sure all graphics card manufacturers start accessing the designated areas thereby avoiding MS getting support calls related to devices sharing memory addresses and causing conflicts.
Old drivers do not of course comply with this requirement.
http://www.microsoft.com/whdc/device/display/agp/UAGP.mspxVia even go so far as to recommend you do not install there gart driver with SP2 and instead stick with the default windows version, although they do say their own version should be ok anyway.
Tried both and for me the default windows driver gave me a severe fps penalty still using the VIA version and no problems.
Anyway rolled back to before installing SP2, updated the ATI Catalyst drivers and installed SP2 again.
No problems at all now and stable as the other 6 computers.
One last thing go into the security centre and if you are running your own firewall then be sure to disable the windows built in one.