I have thought about this too if I ever do enter the 9-5 world of business. I would definitely mention it, and I don't see it as a negative thing.
I've always thought of it as impressive. You've ran your own business, obviously successfully enough to live your life the way you want. It also shows a lot of skills many people lack such as discipline, leadership, initiative, etc...
You don't need to go into specifics about what industry you are in. If you are asked be honest. If you also work in other industries thats even better, tell them about it and just leave out the whole poker thing
