Bug in Start8: Mouse Gesture for Closing Apps Appears on Top of the Screen
Even if you disable Hot Corners you get a mouse gesture for closing an App on the top of the screen. This quickly becomes annoying because if, for example, you're using a web browser and want to switch between tabs, it does nothing until you lower the cursor a bit and select again.
Another thing I found is that when you go into the taskbar to select an internet connection a Metro menu pops out from the left instead of the old menu you got in the taskbar itself with Windows 7.
Otherwise, absolutely brilliant job. Start8 is absolutely worth the $5 asking price.