Thanks for clarifying the difference between Marvin 3 and Marvin SxS in your blog post at Appstafarian. To add another possible use case: To look up footnotes and references in non-fiction literature side by side with the text. For me the hassle with foot- and endnotes is one of the reason why I am shy to use eBooks for scientific literature.
The possibility for tagging notes for further processing is another feature I would need. I've seen that the tagging possibility is already included in Marvin 3! But it didn't work for me. I couldn't add new tags. Marvin didn't save and process my new tags. I've got some other tags generated automatically. Did I miss something or is this feature not yet implemented?
For reading non-fiction I would also need very urgently the synchronization of journal notes over all devices. Have you plans to look into this feature in the near future?
Peter