I don't know what the others think of the concept of MVP but I HATE it. There is no better way to turn off your users than to give them a minimum viable product. I can't tell you how many times I've been asked to review or beta a new product only to find it was an MVP (i.e. it sucked). I never go back.

You only have one chance to make a first impression. Don't blow it. Make sure your definition of viable means "knock their socks off".

Now to your question: There are only three milestones you should care about:

1. First revenue ship. i.e. when people will actually start paying you for your products.
2. Break even. When are you bringing in more money than you are spending (you should include paying yourself in this calculation).
3. Profitability.