My experience with Window 7 so far has been over all positive, but this is not saying that I will not experience something drastic, and that others are not experiencing problems:
1. I have seen reports from friends saying that now that they have gone to Windows 7, Internet Explorer 8 is soooooo slow.
2. Printer driver issues still exist, and HP, on a particular model will not have new driver available until January!!!!
3. Endless reboots on upgrades.
4. Key problems.
5. Download problems.
Also saw this post: Windows 7 Problems Article in PC World