Well, you can run it and see how it looks if you have a source checkout, using `calibre-debug --new-server`.
Currently it is more or less feature-comparable to the current server, except that the authentication UI hasn't been exposed.
Currently, Kovid has been working on the in-browser viewer, which is still pretty rough around the edges but is still pretty cool. No ETA on when that will be done, and he isn't committing on a date to us.
But I have been keeping an eye on it.