I just took delivery of PSCS2 Upgrade and noticed to my horror that for Windows XP it requires either Service Pack 1 or Service Pack 2. I have neither Service Pack because my system works OK without them and one learns to leave well enough alone (unless doing a major technology up-grade).
First off, you should not be horrified. Keeping up to date with security and bug fixes is basic maintenance and part of the responsability of owning a computer. It's people who don't perform basic maintenence and secure their systems that are the primary cause for most of the security issues on the net (no offence, that's just fact).
SP2 fixes some MAJOR
security holes. The fact that you are even connecting to the net makes you vulnerable to what's out there.
I've installed SP2 on a few systems and have had no noteable issues. That's not to garantee that you won't experience bugs but as far as service packs go, this one has been the least problematic in my experience.
All in all, you should not have any issues. Like I said, it's been one of the most stable SPs to date and it fixes some MAJOR
(theres that bold text agian) security holes.
If you have any issues with your printers/scanners simply re-install the drivers. If you see some seriously wacked out stuff, then uninstall the service pack, check you system for viruses and/or spyware and then try agian.
Your plug-ins should work just fine in CS2, I haven't had any issues with any of mine (PK Sharp, NN2, and couple others).
P.S. If it seems like I'm trying to scare you with the security thing, well.. you should be scared. If you value any of the information on that system, keeping up to date with security fixes is mandatory
. No joke.