Definitely a bet. But as a user, and observer of the org, I would buy equity. Who knows what the future brings but they have been doing all the right things and...the gut likes them.
It being a smaller company has its risks for sure. But having the product be their sole focus, rather than it being one among a hundred products of a large company that's ready to throw it away at any time, that too has its advantages - a lesson many of us have learnt the hard way.