If you are a Borgen fan from previous seasons, I would recommend watching. Otherwise, I am not sure. This season is not as good as the original ones, it lost its realism in some way, the political realism which made it so unique and interesting . The main story is good, but the side plots are not convincing and unless you are familiar with the original story they would feel out of context.
The ending lacks as well, as many people mentioned.
The actors are great as always, mainly the main character portrayed by Sidse Babett Knudsen.