I've had this system for a week or so now, and whilst it's graphically very nice and possibly boots faster than Windows 7, the whole dual-system thing for a PC is a bit of an overkill (although you could say you are possibly getting value for money).
Unfortunately the apps available are usually extremely primitive - take the Dropbox one for example : You can't upload or download files; just view them. So if you need to do that you have to use the desktop version...
You can't search for specific apps in the store; the email and web browser apps are primitive too - I hope they will be significantly upgraded in a service pack or something.
There is only one program that has been a bit of a bother - Star Wars : Force Unleased II plays fine. However, it's patch wont run (keeps saying that the program isn't installed). No great loss as I've completed it (multiple times).
Shortcut creation during installation is amusing. Sometimes they go on the desktop, and sometimes on the Surface tiles, but usually not both.
The lack of the Start button is a real pain as it means switch back and forth between the two systems to run an application - plus, it also introduces an extra step to switch the machine off.
However, on the plus side, a scan disk on the boot drive no longer requires a reboot, although I don't think that does the full 5 pass check.
Some of the horizontal bars are hard to see (especially in the Store), with light grey on white not being a terribly good colour scheme.
All in all, its a nice, pretty non-essential upgrade (the only reason I have it is that I needed to check various things work with 8), which needs some serious upgrades.