I've sort of come to a decision. Sort of. I might change my mind in a couple days or minutes.
My tentative decision is to forget about other people's Web 2.0 solutions and instead focus on my own web publishing mechanisms. This means (for now) XML, XSL, and vanilla static XHTML. Any interactive elements should be optional and used only for publishing, not for reading. So I will implement my own push CMS, but it's only a "CMS" in the sense that it's an alternative to other people's CMSes.
Bottom line: do it myself. Roll my own. Own, own, own. I'm a programmer, so I shouldn't shy away from coding. Let the youtubers and myspacers latch their greedy sweet teeth to the nipples of Other People's Ideas. Other People's Web 2.0. I don't need to join the rest of the babies at the McTeat.