Seems like they addressed a lot of the initial gripes people had with the new UI preview. I'm hopeful that similar evolution will be coming to Google Reader.
Google is in the midst of the largest redesign in its history. There may be more to come. Here is a cool talk about this by Jon Wiley, Lead Designer for Google Search: http://vimeo.com/29965463 He talks about GMail around 11min10s
It seems like gmail has previously changed at a glacial speed (for better/worse).
I hope they continue to improve the UX of gmail on a continuous basis.