I waited a bit for SP2, I installed it on my sister's laptop first, saw how it worked, then installed it on mine.
It worked OK for a short while, then I lost the ability to connect to the DSL provider. And I had already deleted the roll back point.
*Dumb*
I'd suggest keeping the Last rollback point on your computer a good long time.
Can't you just cancell SP installation from the Control Panel applet? It used to work on my win2k machine. You just had to keep %SystemRoot% directory untouched. Haven't tried xp, though.