I'm disappointed to say that I share the OP's opinion -- I'm still struggling to find any compelling reason to upgrade from XP.
Win7 is certainly no slower than XP SP3, and may even be a touch faster on my system (but only a touch). But I've yet to come across any function or set of functions that makes the upgrade worthwhile. Win7 may make some techie things easier, but I know my way around XP pretty well by now. And I find XP to be very stable.
My opinion may be coloured by the fact that our household has four PCs, so upgrading is not a £50 decision, it's a £200 decision (as household tech admin, I'm only willing to manage one OS at a time!).
That, and the fact that I'm an old-fashioned guy at heart. The first thing I did on Win7 was to use the Classic Theme and switch the desktop to a plain background colour, make the icons much smaller.... Pretty soon it was looking just like all my XP installations (which, come to think of it, look just like all my Win95 installations.....).
XP until 2014, then, I guess. Can't really see why not.