As a windows 7 user i have to wonder: Exactly why should i upgrade? Does Microsoft have some kind of comparison table between Windows 7 and Windows 10 i can use to make an informed decision?
Seriously though, with classic shell, I like 8.1 a lot, and notice the improved performance over 7... I don't use touch screens, and mostly dual monitor desktop use... that said, it's pretty decent. You may want to hold out until 3-6 months after win10 comes out though...