There are more glitches found in SP2 for Windows XP. One of the flaws could reduce the write speed of most common DVD drives. ROxio and Nero reported performance hits as much as 40%.
Some laptops, battery goes down faster with SP2 installed over SP1. There is also a firewire glitch that slows it down too, but there's a fix for that.
I have to say it sound pretty bad, but in most cases, newer software updates can override most of these inconvienences. Just have to wait for them to come out, if not available already.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?