Hi Daddy Warpig,
I'm the Storyist dev. I'm not aware of any reviews on the ePub export feature yet. I'd be happy to answer questions here, though. And you can download the ePub version of the User's Guide, which was generated by Storyist, from the support site here to check it out:
http://storyist.com/support/
Regards,
Steve Shepard
Storyist Software