When it comes to compatibility issues, GPOs are not going to be your salvation. Sure, certain options could be configured with GPO, but judging by the number of inquiries for reg hacks, I would say that not many companies use GPOs. Not to mention all those still on NT4 domain. 
IMHO, including SP2 in AU is just plain stupid. What were they thinking?
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Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.
