Let's get some things straight.
I tested Windows 7 a few weeks ago (pre-public release beta).
Windows 7 is a vast improvement on windows Vista, and I'd dare to say that it is even better than XP. I do have quite a nice PC, but my ram usage was <1GB. It was certainly higher than XP, but things ran smoothly regardless - even without proper drivers.
Wireless worked right out of the box, which was a pleasant surprise and a vast improvement on XP. You can't very well download a wireless driver on XP if you can't even connect to the bloody internet.
The task bar is neat, and it's bigger so that developers can put more information on the icons given that names no longer show up. This was a much better way to manage space, and one of the things I like the most.
I did not use vista, but from when I've used it on my friends pc (which is better than mine), windows 7 seems more responsive and overall cleaner.
If you haven't used Windows 7, or have only used it in VM, shut the fuck up. No one gives a shit what you think. All posts that are blindly "omg vista sux" or "it looks like vista so its shit" will be deleted, and depending on if I hate you or not I will infract you. Keep this on topic, and don't judge on kneejerk reactions, you prepubescent twelve year olds.