I think the fundamental principles behind release early, release often are sound. I doubt Minecraft would've been as big a success if it'd been released as a fait accompli. The continuous addition of new content is certainly what kept me coming back. In fact, the main reason I stopped playing was that my RSS feed stopped working, which made it seem like they'd halted development.

That said, I can imagine that Minecraft has set dauntingly high expectations for him. He wouldn't be the first to suffer under that pressure. Albert Einstein famously said that his years at the patent office were the happiest of his life, because no one expected him to lay golden eggs.