I priced two 15" PowerBooks, one with 1.5GHz, and one with 1.67GHz. Otherwise, they seem to be exactly the same (after customization). Is the extra 0.17GHZ worth the $165 increase? I will be using the laptop to take notes, view/create PDFs, watch movies (avis, dvds, etc.), listen to music, surf the web, email, etc. No photoshop/3d games/etc. It is, however, really important to me that the comp be as quick and responsive as possible. Will the extra 0.17GHz make a big difference in that regard?