Was gonna report this in the beta testers forum but I *still* don't have access.
Anyways, if you switch on auto hide for the taskbar (Right click on taskbar > Properties > Auto hide taskbar) then when you have a maximized window, moving the mouse to the bottom of the screen should still cause the start bar to appear above the window (this happens with explorer, firefox, convo windows, etc).
But with a maximized plus window (from a script, or the chatlog viewer, or whatever) the start bar never appears at the bottom when you move the mouse down, so to change windows you have to alt-tab.