I upgraded my desktop to Win8 yesterday (or rather I made a win8 partition, I may install Win7 on another partition as well). I tested it a bit on one of the release candidates in a virtual box. Using it the main machine is a bit different. A few observations so far:
1) It is fast. Boot time was noticably quicker than Win7, same with opening programs, especially the Windows8 Apps that come built in which are near instant. To be fair, I have not reloaded all my normal stuff I have running (like utorrent, AVG, etc.) in the background, but I think even with the extra time on that, its going to be noticably quicker than 7 was.
2) I like the start screen. I never really used the start menu myself, preferrring to set up stacks using 7 Stacks. I need to work on the customization of the start screen though and see if it can replace the stacks I used before.
3) I don't like that the start screen disappears when I open a regular program. I have dual screens and I would like to have the windows for programs open on the right screen (which they do), but keep the start screen open on the left since it updates email, rss feeds, etc. in real time there. This may just be a setting issue
4) I like how it easily integerated my my gmail and google calendar into the win8 apps, however it is obvious that each computer profile is really designed for a single user. My wife uses my desktop on occasion and while I don't care if she sees that stuff, but if she wants to see her own stuff, I'm going to have to set her up her own user account/profile. Not a big deal, but just means one more step whenever someone wants to use the computer.
5) I liked how if you use a slideshow as a background the different screens have different background. Pretty minor, but something that always annoyed me before.
6) Took me a moment to figure out how to shut down Win8Apps (like mail). Going back to the start screen was easy, but the apps just hang out open in the background. Unless I missed it, you can't shut them down from within, you have to go to the left menu bar that shows all the open apps and right click and close them individually. Additionally, they don't show up on your standard menu bar like regular apps do, which is annoying to have some apps in one place, but not another.
7) The menu bar repeats itself over the two screens. This is both good and bad. It's good because when a Win8 app is open, while it doesn't show on the main monitor, it does show on the right. It's bad because it doesn't duplicate the system tray for some reason, just the program icons. And since the Win8 Apps fill the whole screen, you can't see anything, which annoys me. Particularly not being able to see the time. This again may simply be a settings issue
If I decide the start screen isn't for me, I can always do what this guy did:
Installed ClassicShell as StartIsBack is still in beta. Computer boots to the desktop, bypassing Metro. Start button is back. I even put the classic Win7 wallpaper back on.
So I basically have Windows 7 again, but with:
1. Faster boot and application times.
2. Native ISO and VHD support
3. Native USB3 support
4. Access to Windows apps (if I ever desire to use them)
5. Sandboxed instances of IE10
6. Much improved Task Manager
7. True copy/paste and cut/paste times
8. Taskbars on all 3 of my monitors, different wallpapers on different monitors
Apparently security is even better, as the Win8 code makes it much more difficult to access the NT kernel for exploits.
I guess this seems more like Windows 7 SP2 to me, rather than Windows 8.
Probably not enough for the average user to upgrade, but I'll probably do that if I decide I can't customize the start screen the way I like it.