There's really nothing wrong with Win 8, it's actually a pretty decent OS as long as you don't use any Metro apps. I run both Win 7 & Win 8 and both work fine for me.
Metro apps are what people really don't like about Win 8 (that and the fact that they can't adjust to not having a Start button). Metro apps run full screen and are very shallow in their capabilities. I removed all the Metro apps from my Win 8 machine and just run the same apps there that I run on my Win 7 machine.
Personally, I would go with Win 8 but since you already have a license for Win 7, it makes sense for you to go with that since it won't cost you anything. Win 8 is perfectly usable but, IMO, there isn't enough pluses there to warrant spending money to move to it.