I installed version 2.3.0 of this module to a ZC1.5.5f site and have noticed that when guest checkout is enabled order confirmation emails are being sent as text emails not HTML. Regular account holders get their confirmation emails in HTML format.
Also noticed that the admin copy of the order confirmation email has the addresses formatted on a single line rather than in standard address format.

I did look through the module documnts but didn't see anything related to this.