Really impressed with wordpress.com. WP remains consistently in the top five companies I would work for, if I felt I had the expertise to work for them.
I’d love to see this administrative backend take root as part of wordpress.org self-hosted installs. I wonder if it’s possible to build wp.org installs in such a way that, if nodeJS and other requirements are present, then you get Calypso. If not, you get the standard PHP backend.