I've been using it off an on with VMware.
In all honesty, I don't think this is a revolutionary change for the good but I think people will get over it. It basically feels like my desktop PC has become this horrid system designed for cloud based environments, you know where everything is throw into the void and some NOSQL-like system is used to sort out irrelevant information.and all I'm suppose to do is click on web based buttons so it feels like functionality exists.
In reality though the back end isn't much different than Win 7 and I think if they just would have put the tiles to basic functionality such as Computer, Control Panel, etc. Thing would make a little more sense. Though they seem to want to challenge users into finding out that you need to right click, select all programs, than find your application, than manual pin the things.
I can relate the "Start" menu for use with launching applications and such, but what is really going to be a pain is if non metro app won't launch from the start screen and if you need to manage two separate task bars. I know Linux has already gone through the wave of disappointing GUI "improvements", but I would ask, if everyone's doing it, why not go with them?