The team at OSE really worked hard to have a great addon to Joomla and MT. It was easy to update and easy to use. Everything is customizable -- from the coupons to outgoing e-mail notifications. It took me no more than 10 minutes or so to integrate with Authorize.net.
Wishlist? None at the moment -- still playing with it. So far, I am a very happy camper.
Would recommend to anyone looking for a billing system for Mosets.