You're correct, Jack. I'll have to be using Moon+ reader on Android for the time being. That's a pretty fine e-reader, if you ask me, although it can't compete with Marvin. Remember that Marvin is supposed to appear on Android later on, too. (Definitely not in 2013, but perhaps in 2014, if we're lucky.)
Besides, I'm not ditching iOS by any means. iPad 3 and Marvin will remain my main e-reader, along with iPhone 4 and Marvin. I also use iPad 1 + Marvin. But I need a
tertiary tablet for my needs. Typical example: I have a book in the original language open on iPad 3, and the same book in a
translated version open on iPad 1. (Compare
this feature request.) If I need to look up something in a different app, such as in a specialised dicationary app, I need a
third tablet for that; it's like having multiple monitors at work. Switching views between the book you're reading, and the other app, just won't do for optimal work efficiency. So, that's what I'll be using my new Nexus 7 tablet for primarily: as that
tertiary "reference" tablet.