I'm thinking about upgrading from my 12" PB to the 15" Combo w/backlit keyboard. Pros? Cons? I have two specific questions also. 1. Battery life on the new 15"? 2. Heat. The 12" gets nice n' toasty (sometimes just while sitting on my desk not doing anything). I know the TiBooks got warm, do the new 15's get as hot as the 12's? Thanks.