Just read the comment you made re: RescueTime. I guess that's the MVP/dry testing tactic. I recently learned about it and am fascinated as well. Getting customers before writing code - a simple, yet brilliant idea that a lot of hackers aren't used to, myself included. The dry testing approach can even be applied to free consumer apps. "Launch" with mockups and screenshots and invite users to sign up for a beta test.

The biggest question I'm struggling with these days is how to even drive users to your barebones landing page in the first place. For pay-to-use consumer apps or B2B apps, you can often seek out direct leads or use advertisments. For general consumer apps, it's much harder to generate a buzz. How do you even get started on driving traffic to something like that?