One big improvement in 7 over Vista is the UI. I find 7 has a better UI and the redesigned taskbar is great. Also UAC is much less intrusive in 7 than it is in Vista.
Though all that being said, I didn't mind Vista at all. I prefer it to XP. Given the choice between Vista and XP, it'd be Vista for me, but obviously I'd take 7 over both Vista and XP.
Pokki is a better replacement start menu than Classic Shell I find.
To be honest though, I've used Windows 8 on my desktop, and I'd still be using it now if AMD graphics drivers and Photoshop worked properly with it. I didn't have a problem with it at all to be honest and there are some things about 8 which I really like. 8 really isn't a bad OS at all, certainly not all 'doom and gloom' and terrible which is how nearly everybody makes it out to be - it's better than Vista in my opinion.