IMO,
Windows 7 (beta) > Vista SP2 RC0 > Vista SP1 > XP (any SP) > 2000 > Vista RTM
But for my tastes, Linux > Windows, just for sheer configurability and flexibility.
- full support for multiple virtual desktops, remote desktop, and remote access
- much less need for antivirus/antimalware/firewall software
- better disk/file management; support for many file systems
- all software updates from a single update app
- much more powerful command-line interface
- compiz-fusion, properly vsync'ed/buffered, completely trounces Aero Glass
- no weird, arbitrary corporate restrictions on system features
- can fit on a USB flash drive; can install or run directly from USB
No matter how many problems I've had with Vista, Linux just works for me, and it stays out of the way when I'm trying to do real work. Even the initial setup is easier on Linux, when you know what you're doing. Reinstalling Vista RTM -> SP1 with all the updates and grabbing all the third party drivers and apps plus all the fixes and patches and workarounds takes me nearly two days just to get my system back into its normal state. Doing the same with Ubuntu (including a year's worth of OS updates) takes me 2 hours, tops, including mounting my data drive, configuring apps, and setting up my desktop environment the way I want it. Heck, it took me an hour (mostly just reading the release notes and a few mouse clicks) to do a system update to the 9.04 beta, with all the requisite packages and libraries and features updated accordingly.
I'm so extremely sick of troubleshooting power management problems in Vista, not to mention the screwed up versions of Superfetch (that hogs the disk, very aggressively, on startup and after executing large programs), VSS/SystemRestore (which hogs disk space and slows normal shutdown to a crawl or takes minutes to even display the interface for creating a restore point), Indexing (which hogs the disk instead of being a decent background task). Randomly wasting 5 minutes at the "Windows is shutting down" screen with the hard drive light blinking away, plus 10-30 second app load times after rebooting, turns a normal troubleshooting process into a total PITA. How can Windows 7 have these features, on the same PC, with the same drivers, without any of the disk thrashing? I know it works fine; I ran the W7 beta myself.
One of the few things I truly hate is the restrictions that Microsoft uses to prevent competition in the OS market. Their OS division should be completely separated from their applications division; software patents ought to be made invalid or reduced in time to < 1 year. The legal madness between office document formats, codecs, etc. is just horrible for the consumer in the long run. Same with the games protection racket. Fortunately, some of this stuff is changing for the better. But it'll be ages 'til Linux will even be allowed to compete as a downloadable consumer OS (meaning, 'til it "just works" with off-the-shelf software, media, etc. instead of with WINE, legally questionable codecs, etc.). Until then Linux requires time/effort/support to make it work seamlessly with other products on the market.
I can't wait until Linux does to Windows what Firefox did to IE.