Maybe a reason for Apple not to simply put in the Merom chips into the current MBP's is that they do in fact generate more heat than the Yonah ones. Of course the increase in speed would be greater than the heat increase, but since there were so many heat problems already with the current MBP's, the slight heat increase may be problematic. Maybe Apple's decision to make the MBP flatter than the Powerbook is now backfiring - the original Powerbook case would have provided more room to assure efficient cooling. It would also have allowed for a bigger battery to keep the MBP battery life on par with the Powerbooks (I still love the 4+ hour battery life of my Powerbook).