Twice in the past few weeks of running Joomla! Beta 2 in my Joomla! New York website that I reinstalled the old one for the latest nightly.
So far in this 12th day, I never encountered any bugs nor reported some bizaare behavior of Joomla Beta2 1.5. In fact, it is running smoothly as if it was ready for final release.
But not yet, as different users have continued to dig into it, posts upon posts in the forums had discovered something that needed to be confirmed nor replicated and even resolved.