From Son of Scooby;
I have been using a Beta of XP SP2 for some time, i have had no problems what so ever. The security fixes that SP2 provides far outweights the problems that may be caused. Any problems that have been located are usualy because of the strict connection controls with firewalls and a few changes with other security features. I'd recommend keeping your computer updated to prevent virus attacks such as the Blaster worm causing havock.
For another opinion check a review at
The Register
it goes into more detail about the ins and outs of the SP.
This is just my opinion so dont flame me.
Toby