There are several good reasons to upgrade to SP2 for MOSS & WSS. When Microsoft releases these service packs its for a reason and that is reason enough for me to seriously explore upgrading. In this case MS tells us that they've enhanced our performance & stability, implemented support for IE8, helped us with indexing reliability and given us yet more stsadm commands to memorize!
But you still have to validate the upgrade won't break anything on your particular system. Here's another reason to have a development box that is all your's that you can break at will.
In our environment each of us has our own dev server in a virtual environment that is not connected to any farm. Then we have a development system that includes our integrated SSRS server and our CorasWorks suite. I am actually thinking of implementing a staging server as well so that during UAT my users are actually working on staging and we can still make changes and tweak things on the DEV farm.
At any rate first I will apply SP2 to my own development virtual farm before doing anything else. Also note there is now a Pre Upgrade Checker. Go to KB article 960577 and check out the list of articles there. Its always a good idea to read up before hitting "enter"!
After reading up you should run stsadm.exe -o preupgradecheck
This is command checks for issues. It does not fix or do anything but output a list. Do yourself a favor and run it before you apply SP2
I'm going to Google around as well and find out what other people's experiences are. When I find something really juicy I'll post it here!