I used to do that too. The most limiting factor for "mainstream computing" is crapware / ads / shifting UX. That's always the reason why average joe neighbors ends up buying a new machine. Random popups slowing down and frustration over 4-5 years adds up to enough for someone to believe that shelling 500$ out again on new shiny will finally bring them the land of click abundance they dream of.
Very few hard requirements are valuable today for most users: battery lifetime, hd video for skype/facetime. And maybe SSD, which are now large and cheap enough for people to switch, and get back the bliss of instantaneous reaction again. Other than that no important task will require more than a core 2 duo. They won't saturate Excel (which was not long ago still single core only). In the case they really do, that spreadsheet is probably worth enough to buy a full fledge MBP.
Very few hard requirements are valuable today for most users: battery lifetime, hd video for skype/facetime. And maybe SSD, which are now large and cheap enough for people to switch, and get back the bliss of instantaneous reaction again. Other than that no important task will require more than a core 2 duo. They won't saturate Excel (which was not long ago still single core only). In the case they really do, that spreadsheet is probably worth enough to buy a full fledge MBP.