I've recently updated the SP2 common issues page on my site to include a few more items which have cropped up during the first few days of SP2's public availability. The list now includes:

Setup
- Service Pack 2 Will not install, I'm told I have an invalid product key
- Service Pack 2 Setup could not verify the integrity of the file. Make sure the Cryptographic service is running
- When trying to upgrade to a later version of SP2 with a Beta or Release Candidate version already installed setup is terminated
- Atapi.sys is currently in use, please close all programs and continue.' Warning Message shown during setup

Outlook Express
- Since Installing Service Pack 2 I can no longer open attachments in Outlook Express

Internet Explorer
- After following a hyperlink to content such as a WMV video file in Internet Explorer it is opened as text in the browser rather than Media Player.

Service Pack 2 Changes
- After install my boot screen is a generic XP Logo rather than 'Windows XP Home/Pro/Tablet/Media Center Edition'
- After install my system runs much slower than before
- After downloading a program from the Internet I am shown a message saying 'The publisher could not be verified. Are you sure you want to run this software?'
- If you attempt to open a file whose extension has been renamed from its true type you will be blocked for accessing the file.
- Known issues with SP2
- EULA text retains 180 day clause

Also a good friend of mine, MVP Mike Kolitz has posted some other good entries about SP2 to his blog a open-node.net

XPSP2 FAQ: How do I stop the Security Center from bugging me about my firewall/updates/anti-virus?

XPSP2 FAQ: There seem to be a lot of people in the newsgroups who are having problems with SP2. Maybe I shouldn't install it?

XPSP2 FAQ: How do I tell whether I'm downloading SP2 for Home Edition or Professional?