I have just installed Thesis 2.1 theme update. This is the official release and not the beta. So far, so good. There are lots of subtle changes and several items have been moved. The menus are a little different too. What I’m most excited about is the release of the upcoming responsive skins. There is a responsive Classic skin included in the Thesis 2.1 update but the forums I read suggest waiting for the release of the Pearsonified skin so this is what I’m going to do. I have not used this update enough to write a comparison to 2.0 but my site still works so that part is good.
You can read more here http://diythemes.com/thesis/version-21/.