Short version - outside of Metro it's basically Win7SP3 and it works great. Metro is every bit the usability disaster that people have claimed when not running on a touch screen.
The good news is that you really don't have to interface much with Metro at all. It replaces the start menu, but it does so in a manner that works with how I'm used to dealing with the start menu already. That is, I already just hit the Win key and then start typing until the thing I want pops up, and that behavior has carried over.
So, yeah Metro is awful for all the reasons everybody has already laid out. Despite that, Win 8 has been a solid performer and I won't be loading Win7 back on this system.
My primary home system will continue to run Win7 until I am comfortable that my production applications will all run successfully (and by that, I mean "games").