Not high DPI-aware, therefore has tiny, tiny user interface, difficult to use on my setup (Windows 7 with display set at 150 %, XP-style DPI-scaling = Yes).
Very unfortunate, because otherwise I like very much the lean, clean and obvious approach of the user interface. The same company has a seemingly interesting pdf conversion and management software, PDF Shaper, which does not suffer that drawback. I hope they take a leaf off their own book sometime in the future.