I've been using Windows 7 as my main desktop for a few weeks now. I love it. There are a few rough edges, but nothing that would send me back to Vista. From the point of view of what you can do with it I've not noticed much different, although I haven't looked very hard to be honest. What I have noticed is the speed. Things happen an awful lot faster. Programs load and run at the kind of rate that they should do on a machine with a 2G processor. File copying and archive unzipping are now happening at a proper speed. People I know are digging out old and slow machines that won't run Vista very well, loading up the Windows 7 test version and turning them into useable devices, which is very interesting.
It used to be that a new operating system meant a new computer. If the final version of Windows 7 manages the same level of performance of the one I'm using it could actually reverse this trend. One of the reasons why Vista didn't work very well in the early days was that some suppliers did a pretty poor job of supporting it with drivers, leading to lots of people with brand new "Vista capable" machines that didn't work properly. This must have made Microsoft a bit upset at the time, but with Windows 7 Microsoft might just get their own back on the hardware makers, since everyone will rush out and buy the operating system and have no need to get new machines.