I bought a Lenovo Yoga to try out Windows 8. The good news is that screens are getting somewhat better on Windows laptops. The Yoga even has IPS, so it has contrast and the colors don't look insane when you look at it from a slight angle.
Many other touchscreen laptops have screens that bounce around when you touch them, which is a bad thing for a touchscreen to do. The Yoga is pretty solid.
I really disliked everything about the new OS, but now I find that I'm adjusting to most of it, and touch on the desktop is the unexpected HUGE benefit.
Overall the "new" parts of the OS feel very rough. In a way, Windows 8 gives me the ability to goof off and to work on the same machine (which feels more like working than using an iPad.) It's not going to be my main machine, though, because it doesn't deliver on work or play as well as the dedicated machines do.
What's Surprisingly Good
IE on a touchscreen! Because two-finger zoom on a desktop browser is just incredible. Of course, I don't use IE because Chrome is actually faster for everything other than zooming, and Chrome doesn't zoom yet. In my opinion, touch without zoom is not nearly as much fun.
Scrolling with your fingers in regular apps, when it works. Sketchup is pretty fun with touch especially.
What's Not Great
Touch almost works on the desktop, but you really can't click anything that's of a normal size. I can't close a tab in Chrome, can't close a Window, and I can't actually hit most buttons in a dialog box. This may be the accuracy of this model's touch screen, but it's very frustrating - I can use remote desktop on an iPad more easily than this, probably because it allows zooming when I really want to click a button.
Because Microsoft didn't spend enough effort fixing the desktop, a majority of the UI is inherited from Windows 7 (like the entire Control Panel and Explorer), which is made up of tiny close-together links, so nothing at all is usable with a touchscreen. There is apparently no gesture to zoom in to click on a thing you really want to, so you're absolutely stuck using the trackpad to click on small objects, which is almost everything.
The ugly desktop: the window chrome is huge and the visual design is completely lacking. It's like looking at a Powerpoint wireframe of a UI, and less customization than ever before. For instance, there is a narrow range of color settings that makes the taskbar look decent at all, and while they give you a couple color choices by default, it's very hard to see at a glance what's going on: which shade of gray is the active window, etc. This set of choices makes the desktop UI tiring to use.
The two-headed hydra of "Modern" vs the traditional OS: the launcher has never previously needed full-screen real estate on the desktop, and it pretty obviously doesn't deserve it. This UI is very half-baked, and it misses on some basic usability. Microsoft could have built a Quicksilver-style overlay view in the desktop mode that allows launching the 4 most popular Modern apps, but they might have also kept the benefits of the desktop UI.
In case this point hasn't been articulated by every single reviewer of the OS so far, I'll add my two cents. On the desktop I always have tons of state in my head, and I usually launch an app to add to it, not to replace it. When I haven't used my PC all day and I go to look something up, that is the time I want a modal UI that asks which task I meant to do, so I don't forget and admire all the old things I was reading yesterday. But other than this single case, I want the PC to be full of overlapping windows and tons of complexity.
The quality of the built-in Modern apps is mostly poor. The finance app and a few others are pretty nice, but most of them are too minimal, and all of them are too slow. On pretty much the fastest laptop I can buy, most of these apps take >5 seconds to launch. Scrolling is often chunky, not even animated. The email app is flaky. I'm not used to the gestures for sharing content from them, so I won't use them very much. I have existing ways to share content on the desktop, and I don't want new ones.
There are extra rough edges, like Modern apps switching in to tell me they need to update while I'm trying to do work on the desktop.
But overall, I'm surprised that I really like touch in a desktop environment. I almost bought a machine with no touchscreen, but it is more fun than you expect.
I wish Microsoft had spent more time making touch work on the desktop, rather than all the effort they put everywhere else. Touch on the desktop is actually a killer feature (not a flashy one) and it deserves more of their effort in the future. Adding multiple ways to do the same tasks (but in a more limited way) is just not useful.
If Microsoft spent all their effort in the next year making touch magical and seamlessly integrating the best of their new apps a la carte with the Windows desktop, they would have a product people would love, at least a little bit.