I'm quite late to the Drupal 7 game, I have to admit it. The reason behind this is a combination of available time, which was quite limited in recent months, and the early release status. I rather wait a while before upgrading my systems and especially client systems to brand new software.
So last week, I started installing my first Drupal 7 sites and gave the whole system a shot. My opinion about it is mixed. Yes I like the new usability improvements, the overlays feel very smooth and well thought of.