Andrew hits upon some of the most critical issues for new startups. Personally, I care about the team the most. If you don't have the right team it doesn't matter what industry you're in cause your chance of success is very low. Plus I'd say you should always keep evaluating your team (and yourself) to see if you're still the right fit. Jettison folks (or yourself if appropriate) whenever it becomes apparent that they (or you) are hindering the business.
It's so hard to stick to a plan like this once you get going; too many external factors you can't control.