I agree that all the current eCommerce solutions have bugs. That is actually why there isn't anything out right now. We are working with WooCommerce devs to make for a great integration into the new Agency theme, and even better building a plugin to facilitate that integration. Then we will work on a few other plugins to handle similar integration with good commerce solutions. Building a solid plugin to handle selling on your site is a lot of work, and it is fraught with problems, as I'm sure you have noticed from the lack of any perfect solutions.
That is the reason nothing currently exists from StudioPress.