I'm making web based games so it is very easy to tweak and re-release (people don't even have to know you've changed it) but there has to be a minimum level of quality and fun to begin with.
Starting with a single, well polished level, and going from there sounds like the best strategy. I can add more or change it based on feedback.
I guess one way to push the release date up would be to cut some of the content and pack it in an expansion pack or later update. But the 1.0 version has to be solid, otherwise no one will stick around long enough for the expansion.