The simplicity of use - it's great if you're new at this kind of thing or have never used such tool before! It has helped me keep track with my fishing trips more effectively than I could do manually in writing down everything myself (I'm not very good about remembering things).
Sometimes there are minor issues that require some attention from customer support as well but they get back quickly enough so don't worry too much :) If your boat lacks GPS tracking devices then maybe consider getting one because otherwise using Sea Log can be difficult without them. Keeping tabs on where we went was always hard when doing manual logging by hand which sometimes led us into making wrong assumptions/errors regarding our location while out boating. Now all these problems got solved thanks to sea logs since keeping up-to date records became easier due its automatic nature compared to what would take hours during other methods.