[TuaAmin13]

I agree. If this guy is a customer instead of (friends, family, etc) for private beta, he's going to represent part of the people paying you for this.

Congratulations. You're basically getting early feedback by someone who really really wants this. He wants a beta to use in production, and he knows that. That's how much he wants it.

Lay down the ground rules as far as production support and bug fix turnarounds based on what you can manage without trying to spend every waking minute keeping them happy. They may not get every new feature request they ask for, and , like you said, some UI might change.