I was VERY unsure about going to W7 seeing as I was so frustrated with Vista. I really didn't want to spend my hard cash on another white elephant.
However, I now realise that it's the little things in life that make you happy. :)
The first thing I encountered in W7 that made me REALLY happy are the desktop wallpaper options.... I know I know, that's not exactly important to most people. But to me it's a real blessing. You don't just have Strech(pointless option), Centre and Tile, but you have have "Fit"! meaning you can keep the aspect ratio on an image, but have it fit your screen, no matter how big it is! I know, I know, I'm a geek, but I've been waiting for that feature since Win 95!!! I'm a serial wallpaper changer! what can I say! :) Not just that but the dynamic slide show wallpaper was not expected but VERY welcome! I have my recent photos of my baby boy cycling my desk top now.
Aesthetics aside, there is also the speed of the thing! It's MUCH faster! and you don't get so much clutter all over the place! and random pop-ups are almost a thing of the past. Booting is faster, and shut down works much better!
There are tons of other handy features, such as the re-invented task bar.
Ability to change the UAC to be less annoying or more secure is a massive bonus. Catering for the paranoid and those that just don't care alike. :)
If you have Vista, trust me! you will be glad to get rid of that camel with only 3 legs, and get yourself W7.