In a sentence: Windows 7 is the most promising effort I've seen from Microsoft in a long time.
Is it perfect? No. What is? Show me ANYTHING that is "perfect". I've never seen "perfect", ever. But my experiences with Windows 7 on a mix of good and crappy hardware have been very impressive. One computer, my wife's Dell Dimension 4600C mini-tower, had an issue recognizing the USB Linksys Compact Wireless-G device. But that was only a matter of sticking the Linksys driver install CD into the tray and pressing Enter. Beyond that, it's working like a champ, and on 1 GB of memory. I also have a Dell Latitude C610 laptop with 1 GB of memory that runs Windows 7 significantly better than it ran Windows Vista Business edition. All of my computers boot faster, login faster, launch applications faster, close them faster, log off faster, and reboot faster. The interface is cleaner and simpler. The UAC is simply not an issue anymore. It's less obtrusive than the implemention on Ubuntu 8.10, Fedora 7 or Suse 10.
While the new Task bar gives me mixed feelings, I'm getting used to it and no longer pay attention to it. Once I set the Taskbar buttons to "combine when full", it's actually very user friendly. I still don't like IE8, but I have been using Chrome almost exclusively anyway, and it's easy as dirt to download Firefox or Opera or whatever you prefer.