I'm in the same boat as Joel. I've had projects on my to-do list for months that I've never got round to because in my head they were massive and I didn't know where to start. With daily shipping I've started to break them down into tiny tasks, so even if it's just registering a twitter account that takes 10 minutes, at least it gets the ball rolling on the project.
I expected that the new TLDs would cause a lot of confusion for people but I've not noticed any issues so far. Our domain is .work but even people who aren't that tech savvy haven't had problems visiting our website or emailing me, after I've told them what the URL is
I've not been in this position, but I imagine I'd feel pretty guilty. However, the 2 founders probably have quite different early audiences which means the early feedback they both get could be quite different, which ultimately means 1 year down the line, the two products could end up really different anyway!
Something else to consider is physical vs digital products. If I buy a physical product for 9.99 and I give 10, I get 0.01 back. The cashier actually gives you something back that you can put back in your pocket which makes you feel better about the purchase. This doesn't happen online though. If you charge $9, I can't pay you $10 and get $1 back. So a whole element of this psychology is missing in digital products
If you want to make $$$ then probably not, but if it's just a side project then go for it. Depends on the size of the group you interviewed too. And depends on how much time/effort it would be for you to make
tl;dr it depends 🤷♂️