I find that shutting it down and even putting it on standby requires too many actions.
Metro app's don't fit in with the desktop version, they should run as a desktop app. Running a metro app breaks the Windows key which instead of bouncing you between desktop and the start screen will bounce you between the metro app and start screen..
Multiple monitors. Windows 8 corners become iffy on the join between monitors. (Why not just remove these hover areas?) The start screen seems to randomly choose a monitor to appear in. For some reason my right monitor doesn't have the clock. On the desktop, both monitors have my application icons at the bottom yet the program opens on the last monitor it was opened on instead of the monitor in which you press the button.
I love the start screen. I think its so much better than the Windows 7 start button. I think Windows8 is alright in the same way Vista was alright. It was better than XP but had a bunch of annoyances. I can see why people like Windows 8 but I can't see why anyone would say they love it.