Don't do it if you use CS2 or lower. (Photoshop)
I don't like CS3, so I use CS2 (it's less bulky and uses WAY less resources.) Anything not CS3 has some serious issues with SP3. And Adobe's offical answer to the problem is... "Use CS3."
Causes memory leaks in CS2
SP1 on Vista on the other hand, well we're still having issues