Windows 7 is a definite success (when compared with the dreaded Vista!).
I have successfully installed it on many 3-4 year old pcs and laptops, the results were amazing. The machines have never run as fast (even compared to XP). It doesn't hogg resources like Vista. It is fast, responsive and visually impressive.
It has been greeted by the tech population with mixed reaction (this is normal - XP was scorned until 1 year after release), although the many users I have converted to Windows 7 will tell you that finally they have an OS that makes computing fun and easy!!
I have been testing since RC1 (build 7100) and I have a reliable, fast OS that allows me to USE the PC and makes my time productive - not like earlier MS offerings which I seemed to spend more time trying to get working!
On the hardware side - I have taken lots of older hardware and obscure products and Win 7 just auto installed drivers! No hassle, no head scratching.
I have to say that AUDIO devices are the only hardware driver issues I have come across so far. Having said that, I managed to resolve the issues quickly.
The built in diagnostics have been VERY powerful. Prior to Win 7, if a troubleshooter popped up it could be guaranteed it would fail. Now I am happy to allow the wizard to resolve the issue as I have found it to be 70% successful.
Win 7 makes networking easier, the homegroup feature is a definite bonus, media streaming and even a simple "snipping" tool for screencaps makes this OS a delight to work with.
DVD/CD burning works with 2 clicks and the new taskbar and windows features are very fast and responsive.
The Library feature is very powerful. Its basically a virtual folder in which you have links to your frequently used folders.
Check out the new Windows Live Writer and Gallery! (You have to Download from Live.com)
The one failing on Win 7 is the new Search. This is very frustrating and time consuming.
All round tho - Thumbs Up for Windows 7 - ENJOY!!