I have used EndNote for the reference citation for years and it is really getting more and more powerful nowadays.
However, I found that it is still difficult to use it as a reference manager to organize all of our reference (PDF) files. It is necessary for us to sort the reference files in different groups and each group should be able to create their own sub groups, and even deeper layers of sub groups is demanded. For example, I may create a main group which content four sub groups named organic, inorganic, analytical, physical. In the layer of “physical”, I may create sub groups such as photo-physical, thermodynamic, and then again create more sub groups under photo-physical. It’s much continent if we can organize our PDF files this way. As I know, Mendeley they provide this function. Hopefully, EndNote will be able to provide this function later.