In beta at the moment, but this significantly softens the learning curve for restyling MT blogs. Notes about it here.
Movable Type 4 has been quite reasonably criticised for being overly-complex to work with, since the default templates are full of conditionals and in places appear to have descended into tag soup. In practice it’s nowhere near as bad as it seems, and the complexity is more due to the flexible nature of the tools than anything else. But we’re starting to see simplified and alternative template sets.
There are still performance, usability, and documentation problems – but I’m far less tempted by switching to WordPress than I was before. Also of note: it feels like mailing list traffic and excitement has picked up quite considerably since the release of MT Open Source 4.1.