I'm something else. Definitely not a mumblecore fan. Just ask Jason.
I looked at the Wikipedia "List of mumblecore films."
Mutual Appreciation (Bujalski)
Quiet City (Katz)
In Search of a Midnight Kiss (Holdridge)
Cold Weather (Katz)
and at least one not listed:
I first heard of mumblecore from a Film Comment article back in 2007 or 2008. I didn't actively search out any of these films, but I've slowly come across them over the past few years.
I think I love the work of Bujalski and Katz.
The other guys, I'm not so sure. It's pretty clear (as mud) that Greenberg and Cyrus are actually straight-up Hollywood films with roots in "mumblecore" and not mumblecore proper, whatever that is. I haven't seen any Swanberg films yet. He seems to be the other mumblecore giant.
For what it's worth, I agree with Bujalski's assessment that the label is probably "a little reductive and silly."
I think that there are a bunch of us coming up now who have many of the http://www.blogger.com/img/blank.gifsame influences, and the same anti-influences, i.e. some of the crummier aspects of the indie scene that we'd all like to bury. My new film, "Mutual Appreciation," premiered at South by Southwest, and there was some talk there of a "movement" just because there were a bunch of performance-based films by young quasi-idealists. My sound mixer, Eric Masunaga, named the movement "mumblecore," which is pretty catchy. I quite liked those other films that I saw, but I think it's probably a little reductive and silly to actually group any of them together. And if it is a movement I'm sure I'll want to get out of it and do something else. Again, not much point in making films that other people have already made, unless you've got something new to bring to it.