I don't see a reason to disable it to be honest. It gives me an additional multiplier when overclocking too.
Apple should have had quad cores in the iMac and MacBook Pro since since 2008.
Me either, but I have seen stuff like that on my servers disabled out of the box (not exactly the same, but you get my point).
I could see Apple using these chips in their iMacs and waiting till Arrendale for the mobile systems. I could also see Apple waiting till Arrendale then upgrading their entire consumer lineup with nehalem all at once.
MCP99 anyone?
Good call. It will be interesting to see how that all pans out.