You'd probably be surprised at how new/young we are, but I appreciate the unintentional compliment :)
In reality, we've been doing this outside of our 9-5s for a couple of years (with the majority of the "we" coming together while trying to build a few internal projects).
Most of our dev team has been full-time for a bit over 1 year now.
Start-ups are rough and when you're bootstrapping through consulting, some months are great, and some months are rough. I kept my full-time to feed in money during the bad months to keep the machine growing at times that I knew it was in the right direction. I had that job up until a little over a month ago.
The full-time job was actually great (consulting at the US HQ of a top-tier German car company, ironically enough) but I'm awful at working for someone else, there was too much talent and goodness brewing behind the DarwinApps team, and I was clearly the bottleneck. It's not easy doing something like this while you have a 9-5, but if you're young and single, it's doable. I'm not saying it's not doable otherwise, just speaking from what I know.
We are by no means a success just yet, but most of the core team is finally in one of two offices, working on the same problems full-time. It's a beautiful thing, but it's by no means a success just yet.
That being said, a lot of awesome people helped me with advice along the way. I'd love to help if you have any specific questions, think I could answer them, and if you think it would help progress your company in the right direction. Feel free to email me: Vlad (at) DarwinApps.com