Is a substance designer material add-on for blender worth it?

I am not sure if it is worth the hassle / money vs simply working the exported image maps with the free bridge software.

You are talking about this one?

The fact that you have access to all the procedural parameters directly inside of Blender makes this pretty powerful. If you use Substance Designer files and have an library already this is pretty valuable I would say.
But ultimately you have to make that decision, do you need the access to the parameters directly in Blender or not?
For me it would boil down to that question, and right now I have no use for it since I am working in UE4 (which has a similar add-on, which I also don’t use).