I subscribed for a brief period. The main draw for me was that they have the ELCA (Lutheran church) records. Unfortunately, they had not yet added the areas that I needed yet. It was worth it for me to get those records, but from what I have seen most of their other records can be found elsewhere, and sometimes for free.
So, the short answer is that it could be worth it if there is a certain record group that would be useful in your research.