The lean start-up would say: - launch early - test with your users what needs fixing - fix it (and don't bother fixing the stuff that the user's don't care about).

I think there is a legitimate caveat to this though. If you're app does something where failure leads to death or some other really bad outcome (might be medical software), then being super lean is probably not advised. But in the main, launch early, test, fix and repeat.