I've been using it for maybe a month since trying it and being really impressed with the startup times. I've finished installing everything I used on win7 and more (vs2012 for example) and it's retaining it's impressive speed.
I haven't tried multi monitor yet, but I had thought about that problem, metro really is pretty awful, I don't mind it when I tap the windows key and start typing to find the program I want, but I don't use it for anything else, and it annoys me if something causes it to come up.
The only real problem I've had is sometimes that search box doesn't clear.
[winkey] ecl (enter) (eclipse)
[winkey] note (enter) (notepad++)
and it ends up with "eclnote" which doesn't hit any search results.
how the hell did that get through beta testing?? admittedly it's sporadic, but seriously why is the search box not cleared every time metro pops up?