Is there a reason for announcing it now, when it's incomplete and less useful, rather than once it's done (or more feature complete, at least)?

I ask because this seems like the sort of thing I would look at, then shrug off because it's not all there, as I don't want to put time and energy into learning a product that will have the features I want "some day", so I'd be likely to skip out on it for now and then forget about it basically forever.

Personally, I'd much rather be shown something that feels "done" and try to integrate it then than work with someone's first pass on the implementation, and I'm concerned that others would feel the same way and you would miss out on users.