I've been running the RP on my multi-monitor desktop, and I haven't seen any issues with the hot corners being unreliable. In fact, if you set the taskbar to auto hide, it seems that the hot corner with the 6 pixel "curb" is actually easier to hit than the start button.

I haven't had any problems making the transition, because I use the start screen exactly the same way as the start menu. I either hit the Windows key and start typing, or I click an icon that is pinned to the task bar. In Win7 I never actually used the MRU list in the start menu, and I equally never clicked into the all programs list. If it was important, it was pinned, and if it wasn't then search is your friend.