There's not a huge reason to upgrade unless you won't to. That's pretty much always the case for the first few years of new OSs until new dirextX filters into cheaper gfx cards and many many games use it. Personally wouldn't touch win7 now it feels outdated and for media consumption it's frankly crap. Give me mail, netflix, audible etc on metro. I still have an identical desktop to win7 for everything else. iOS/android do these sort of apps far far better than the desktop equivalent, so now windows can do these sorts of apps as well is fantastic and if you don't use them, well you haven't lost anything and gained a large amount of under the hood stuff. As well as better licenses and prices.
However if you have to buy a new computer or a new license, then you are mad to not go win8 (expect for a handful of people running very specific software that might not be compatible, like in house company software)
Not only does win8 have far more benefits, like for like its far cheaper due to the license having significant differences.