As far as all of our analytics tell us over the past year of being in Beta, the new UI is far more stable than the old UI in terms of crashes and hangs. But this was as an explicit opt-in (nobody got it turned on automatically) so that was another motivation for getting this in front of new people. We are essentially smoke testing for both stability and usability while it’s still a Beta Feature.
Folks may be taking the “early June” target too literallly. I think realistically we are about 6 weeks away from today. It’s ambitious, for sure, but I am optimistic we are going to address the majority of the most common feedback we have seen here.