One of the most interesting finds so far is that the MacBook Pro's Core Duo processor is soldered to the main logic board, rather than on a socket, and therefore is not not upgradeable after purchase. The only way to upgrade a MacBook Pro to a faster processor is to select the 2.16GHz (+$300) option when ordering a 2.0GHz MacBook Pro Core Duo from Apple's online store.
Source: AppleInsider