Hello Developers & the Forum,
I just wanted to share that I just completed a research paper using MarginNote 3. A big thank you to the developers for creating this wonderful tool!
I had purchased MarginNote since it was very first released, but have only recently put it to use. I have yet to use all its powerful features, and for the most part, it was a wonderful experience.
The features I mainly used was highlighting and making notes.
When highlighting text in a PDF, the OCR feature proved itself outstanding- even for PDFs that were previously scanned.
The note-taking layout exactly fits with the way I work with research papers. I liked taking notes in a dedicated list view which is always open so I can refer to other notes I make on a highlighthed quote. In other PDF annonation apps, you have to make notes in a tiny text box that closes and is out of view when working on another note. I appreciate the time and effort the developers put into MarginNote to be able to do this. Once I wrote the note, the ability to give the highlight and note a title was really helpful. I do not know of any other app that does all this! 
I also came across a few bugs that I will post separately about, but they did not get in the way of doing my work.
Thank you again developers! I hope you are around for a long time to come!
Cheers!