Well 0.9 is out. The main issue I'm seeing is people complaining about extensions not working - they wanted to go from 0.8 > 0.9 and still have all their extensions. This was never going to happen due to the overhaul of the Extension Manager, but that fact should have been made a lot clearer where ever 0.9 was offered for download.
Anyway, I've just been scanning through u.m.o. and picked up a few new extensions. I fully support this way of creating a browser - picking and choosing your functionality is a great way to go about things.