Nope, but I very much respect MapleRead. I have purchased all 3 versions of it. It's possible that MapleRead may already be better than Marvin at this point.
However, I'm primarily interested in a
cross-platform solution (for example, I only own an Android phone), so my main hope currently is BookFusion.
I'm very happy with the feedback provided by the BookFusion developer in that BookFusion thread, so it does look hopeful. He's familiar with Marvin and wants BookFusion to outdo it in all respects.
I've already submitted some
specific feedback to him, listing a few features in which BookFusion currently still lags behind Marvin (such as no swipe up-or-down gesture in BookFusion, for adjusting screen brightness), and I'm hopeful these features will be added to BookFusion later on.