One of the most useful features of Devonthink is full-screen reading. Since we keep almost all the documents in Devonthink it seems just a basic requirement to be able to read them in a distraction-free fullscreen mode (And Devonthink delivers on that).
Unfortunately, this is not the case on Devonthink To Go. There is not fullscreen support, at least not for the PDFs and RTFs that I use.
This is kind of a necessity, both for reading and for presenting (there is a thread about that as well). While for presenting we can send the file to another app, for reading and annotating we can’t (or we have to reimport the document after each and every annotation).