I have been using for a month or two now and the platform seems pretty stable. Updates come through every day and it's like a lucky dip as to what is going to appear/disappear.
Aero appears then disappears and then reappears. Yesterday a box with MINEFIELD appeared at the top left corner. This is supposed to replace the standard window title in the Firefox 4.0 UI mockups - at the moment it's just placed underneath the standard title, this means that it had a line of mostly wasted space.
JoeClark replied
396 weeks ago