Works well for me.
Going out on a limb here, but I've found Win8 has actually improved my workflow, the trick is how you use it.
I'm a 'heavy' desktop user and run a pretty standard setup with nice chunky widescreen for getting stuff done and a 4:3 panel off to the side.
The thing that TIFKAM allows you to do is park all your social & media stuff under the one hood and keep it contained.
When I need to get work done, I send Metro over to the second screen (tricky before you get the knack), where it can sit there and bleep away with it's tiles/webmail/Facebook/YouTube/whatever.
Meanwhile my main desktop screen has fewer windows open, less clutter and is more focused.
For what it's worth I've found having a clean and obvious seperation between work & play helps keep me on track when I need to, but still has my life accessable with flick of the eyes or the mouse.