It's ok on my laptop (not touch-based), but the issues really start getting rough if you add a second monitor in. There's no good way that I've figured out yet to move the start screen or any of its' metro apps to the other screen - they're just stuck there. When it's just one monitor, going to the desktop at least removes you from the Metro interface.
I haven't tried it on a multimonitor system yet, but my understanding is that the start screen and apps will appear on whatever monitor they're launched from and can then be moved around ( http://blogs.msdn.com/b/b8/archive/2012/05/21/enhancing-wind... ) - is that not your experience?
