After I disabled the desktop effects I'd been playing with I see that the windows get focus as you alt-tab, but I don't see any flicker (also i915 but gpu on a second generation core cpu).
Well, I think the perception of 'flicker' or not depends what colors your windows are using.
With windows that are mostly black text on white background the matter is not as bad ...
I don't have any problems with the taskbar dissappearing ... I presume yours is not just set to autohide ;-)
It is intentionally set to autohide. But it always comes up (and covers part of what I want to see...)
I don't think this is really an "upgrade warning" btw so I suspect this thread will be moved soon to the Software section.
Well, slam asked me in the chat yesterday I should post the issue and I didn't know where else to post it ...