I don't know of anyone who has bought Scrivener and hasn't loved it. Great for the editing process, too.
My mom didn't like it. Boo. She doesn't write books though. And I doubt she was willing to get past the learning curve.
Scrivener is a lifesaver, though, I agree with that. For the Fantasy Historical fiction where it did require a huge cast despite my efforts to keep it under control, I was able to make profiles for the characters, make a template for the character profiles, keep track of settings, research and PDFs. This means less screwing around on the internet with the excuse that I don't have a particular fact or visual cue. I love it for world building--helps me keep track of the things I said and the internal logic, even if the reader doesn't need to know the internal logic in the world building at that point, it helps me to keep track so there aren't inconsistencies later.
Since I have to keep track of four different countries over a time period of 200 years, it really does make organizing the info so much easier.
So far 34 characters for three books.
BTW, Fantasy doesn't always require a large cast, that's epic fantasy. Urban, Contemporary, Slice of Life (Yes, you can do slice of life), Paranormal don't require large casts. You can get away with only a few characters.
Historical fiction also requires large casts, often to get the historical accuracy right. But often authors manage that by hand waving a bit. I'm hoping to hand wave too. So I can mention a name and then it not be important after a point. Ya know, like real life.