@dentaku: The Start Menu is a case of "move a mouse pointer into a corner and things swish out". There's really two issues, from a UX POV, with what they did.
1. There's no visual cues or affordance.
2. The hit area, in some cases, is simply too small. Fitt's law is great, but it doesn't work reliably here. Remote sessions means the UI could be windowed and there won't be an infinite virtual space to try and hit, and the same sort of issue occurs with multiple monitors.
Like I said, there are problems with what Microsoft did. I'm not trying to be an apologist. They need to fix this. It doesn't mean they have to through the Win8 concepts out and go back to the Win7 way of doing things. Providing the ability to optionally behave like Win7 isn't really addressing the problem, and isn't what they should do.
Actually, with multiple monitors, the corners are "sticky". If I throw my mouse into the general direction of the upper right corner of my left-most screen, it will stick to the corner as long as I hit the upper edge (which is not adjacent to another screen) first. So as long as you don't have monitors on all sides of your main one, it's not that hard.
There are a few other problems I have with the hot corners though:
The top-left and top-right ones are competing for things you would otherwise try to hit using Fitt's law, like the window close button and system menu. For top-right it's not such a big problem, because the charm's bar won't cover the corner, but for top-left I often find myself accidentally covering up IE's back button by bringing up the app switcher by mistake.
Ever used the Metro RDP client? Even though it's full screen, the hot corners will still belong to the host system. The start screen and charms bar etc. of the remote machine can only be brought up using the keyboard and the app bar (and if their contents are very similar, that's bloody confusing).
Using the hot corners on anything other than your primary monitor will move the start screen and all metro apps to that monitor where they will stay until you manually move them back.
As for affordance, I can sort of see the rationale between the removal of the start button. The idea is to pretend that the desktop is just an app and not special (even though it is still treated specially in reality). None of the other apps have a start button, so why should the desktop?
But some more visual clues would definitely have been nice.