Im now using windows 7(after staying up till 3:20 am in the morning yesterday setting it up). I really like it. It is the fastest and easiest to use operating system I have ever used. It required some tweaking(less than any other os though), but this is expected given that I want it to fit me perfectly, and now it does.
7 is faster and more responsive. My bootup in Vista was around 1:15, and 7 was just 37 seconds(although to be fair, Vista was a used install, and 7 is brand new). It uses less ram too. It idles at around 940 mb of ram, as opposed to just over 1.5gb ram in vista. this, combined with a better desktop manager, speed everything up a lot!
Jumplists are great. being able to right click my browser icon and open a page from the history is neat. The new taskbar is a little big, but im used to it now. I like being able to reorganize window order on the taskbar.
All in all, the new features are great, but the massive drop in resource usage is the big plus.