Curses, our secret plan has been uncovered! Canonical is indeed trying to degrade Ubuntu, make it less secure, and drive average business and personal users away. The orange star icon was a paragon of obviousness and clickability, so it just had to go.
But seriously, we did not design this behavior yesterday on the back of a napkin. We discussed it publicly at the Ubuntu Developer Summit in December. It's part of a long-term plan to clean up the notification area, and in particular to stop using it for things that it cannot actually recognizably notify people of. If you have learned to both notice and recognize the orange star icon, then I'm sorry that skill will no longer be required, but we think making update installation more obvious will make Ubuntu more secure for more people.
Of course the new behavior is a bit rough around the edges, but the problems are fixable. As I write this, the auto-opening interval is being changed (now that we know it works) from two days to seven. Compiz needs fixing so that when windows open unfocused (as Update Manager does when it opens automatically) they're in the background too. And any patches to reduce Update Manager's memory footprint are more than welcome.