I see nothing wrong with in-app purchases, even if it was for buying features. And I'm surprised Kris now wants to keep Marvin free, whereas he originally wanted to sell it. Of course it's great news for book lovers, but it almost seems unfair towards Kris, given all the hard work he put into Marvin, bringing us more quality and enjoyment within a few weeks than some of the world's largest mega-corporations with thousands of employees were able to do in
years.
Here's a funny story... a friend of mine wrote me yesterday he created a new verb in the Slovak language,
marvinizovať 
(meaning
to marvinise). He said he was so excited about us finally getting, in Marvin, a competent EPUB reader for iPads, that he's now spontaneously and enthusiastically started to convert some of his old PDF files into EPUBs, just for the pleasure of being able to read them in Marvin.