It seems like Apple is going in a pretty obvious direction. Whether it be strictly for aesthetic/form or to force us to purchase replacements more frequently....it seems like they are quickly abandoning any sort of upgradability in their next gen systems and I think it's only natural to expect that this will be their new norm (hopefully mac pros aside!?). How important is it to all of you? How often do you upgrade your laptops (MPBs)? Desktops (iMacs)? How often do you keep your computers on average? Is it even worth it to upgrade? It would also be helpful to know if you have any other computers in the house and how you use it (photographer vs student vs stay at home mom).