The biggest offenders seem to be the "name brand" computers (Crapaq, HP, Sony, etc.) and this revolves around driver updates (usually). Some of these machines want you to upgrade certain drives before installing SP2, and some after (hell, some are a mix of before and after!!)
My Asus mobo/AMD 2600+ setup is actually booting and running faster with SP2, and hasn't crashed since the install!
