I'm probably a little biased, but to me this is one of the most important and impressive releases of free software in a long time. Tablets are getting to be the new prison where consumers are kept inside one ecosystem with no way to move to another platform with his/her data.
This release means that there is now a way to use tablets while keeping control of your own data. And they managed to make it beautiful and even come up with a new paradigm (activities) in the process. Kudos!