IBM's large number of Web applications will need to be tested and some modified to work correctly with SP2. Currently, some high profile, business-critical applications are also known to conflict with SP2, IBM tells its employees in the note. When the current issues and concerns have been addressed, IBM will deploy a customized version of SP2.
InfoWorld

It's been a long, hard slog for Microsoft, and now it's time for customers to feel the pain. Analysts say that customers must expect some drama when they install the service pack, which makes changes to the operating system itself.
Microsoft's XP SP2 Arrives
internetnews.com