Adam Kalsey is a pretty serious Movable Type developer. MT has gone through some recent upgrades and Kalsey adroitly breaks down who new features are aimed at: developers and businesses. He's going to be moving his raft of plug-ins to the new system on an as needed basis, essentially choosing a conservative path. He's right though, that SixApart has stopped innovating.
Frankly, no one's really innovating on the authoring and publishing side of blogging. We've still got the same crappy forms on the Web side, and there really aren't even that many desktop blogging tools. And since the trackback, name a new feature on the published page side?