I have been running the Windows 8 Consumer Preview exclusively since shortly after it was released. Overall, my experience has been great. I love the new Start screen and live tiles. I love that the OS is snappier on my Vista hardware than Vista was (and I was never dissatisfied with Vista). I love the Metro apps (I'm very fond of Metro IE in particular). I think it's great that, at least on x86/x64 hardware, you can still develop and run desktop apps if that's what you need, but use Metro apps whenever you can.
I'm running the OS on a notebook with no touchscreen. I've had little problem adjusting to the new methods of accessing things. Heck, I even found myself trying to use the Metro IE back button (the one that fades in when you move the mouse near the left-hand edge of the screen) in desktop IE recently and was momentarily lost when it didn't appear!
I love the way the desktop works. It acts as an app, just like any other app. It can be shown side-by-side with another app if you like. If you're done using it, you can flick it off the bottom of the screen to close it. If you spend all of your time with desktop applications, you'll be right at home there. The only real difference is that there's no Start button in the lower left corner. But if you go to that corner with the mouse, you can click on the Start screen tile that pops up and you're at the Start screen.
Things I think need improved
The option to shut down or restart is inconveniently located. I don't consider shutting down to be a setting, but that's where it's located. Of course, I guess it's not that different from clicking "Start" to shutdown as you do in current and previous versions of Windows. I think it would make more sense to access it by tapping on your user information, since "Lock" and "Log out" are both there.
The "favorites" mechanism available in desktop IE isn't directly accessible from metro IE. As you type in the location bar, items from your favorites appear. You can also pin sites to the Start screen from IE, which is an OK substitute, but if you have a lot of favorites that you want easy access to, you're going to have to pin a lot of sites to that start screen and there's no real organizational structure at that point.
When you're on the Start screen and it is wider than the visible area, you can scroll left or right by "pushing" against the left or right edge of the screen. Unfortunately, you can't do this in the preview apps available at this time. This also isn't the default when developing a Metro app. I haven't done any digging yet to see if this is an option you can easily turn on in your apps, but it sure is inconvenient that it's not there by default. It makes things feel kind of unfinished and inconsistent. This is the biggest issue that I see at this point, believe it or not. The OS as a whole feels pretty polished to me, much more so than the developer preview was, so it's just surprising that I see this behavior.
Now, the preview apps lack some of the polish I mentioned above. The mail app is fairly nice looking, but it suffers from real estate issues at times. I would like to see the ability to "minimize" the accounts and folders and be able to access them without having to go to the app menu. We also need the ability to change the way the app checks for mail (such as having mail show up as it arrives rather than at some predetermined interval, or being able to change the interval). It also needs to be able to recognize that mail has been read elsewhere and adjust the live tile and lock screen count accordingly.
The music, picture, and video apps are nicely done, but I want to see the full Zune experience built into them. I'm a Zune Music Pass subscriber and believe that this should be accessible from the Music app. As it is, I have to have the Zune desktop software installed to download and play music, as well as to select my permanent downloads (I'm still on the older Zune Pass that includes those 10 free monthly permanent downloads).
I've found issues with a couple of pieces of software I've installed, but I expect those issues to be corrected by whomever needs to correct them either before or shortly after Windows 8 ships. One issue I had is with the aforementioned Zune desktop client software. When I set up my Samsung Focus S (Windows Phone 7.5 OS) to sync with it, I was unable to set up wireless sync, apparently due to something still missing in the OS. I play a few PC games and use GameStop to maintain some of them. Two of these games won't install under Windows 8 because it claims the OS isn't supported; however, I was able to install and play a couple of other games.
More stuff I really like and in conclusion
As I said earlier, chrome-less and plugin-less IE rocks, though the lack of a way to kick it into compatibility mode has forced me to use desktop IE a couple of times (sigh). The calendar app is terrific and I haven't found anything wrong with it yet. :) The messaging app is also great. I like the weather app, but sometimes it seems to forget that it needs to update it's live tile.
I've seen a lot of hand-wringing and wailing and gnashing of teeth over the major changes coming in Windows 8. While I understand the skepticism, for the most part I disagree with those opinions. I see the changes as a good thing. I know I'm a geek, so I may not be the best judge, but I've been quite comfortable using the OS on a non-touch device. There was a massive amount of the same hand-wringing and skepticism when Office 2007 was released and we were introduced (some would say subjected) to the ribbon. I was one of those who was skeptical. Fast forward a couple of months of use and I changed my tune. I got used to the ribbon and it actually improved my experience with Office. The change to Windows, while probably just as disruptive as the change to Office, will probably change people's Windows experience for the better, and I don't believe it will take as much time and effort to adapt as the change to Office.