WP 3.0 is supposed to be the *next big thing*. For one, it will finally have a feature movable type has had for years, multiple blogs under one interface. The WPMU project was not really easy to install.
Anyway, until then, the big changes are on hold.
I’m kinda in the same boat, I’m looking to switch to Melody which is MT based and just released its first alpha. MT has grown kinda stagnant and MT 5 has not gotten great reviews. Melody seems to have the community support and should be an easy switch from MT 4.2x.
I like the multi blog, I’ve used it to create a separate gallery blog (now broken and stagnant, unfortunately) but the big thing is being able to play with layouts and stuff on an offline copy of my blog.