I think it may depend on the breeder. Greenhouse Seed co. claims that their Fem seeds are 100% guaranteed to be fem (not hermie or male), but they could easily blame any hermie reports on the grower. I am using some right now (Great White Shark), and I have no problems thus far {knocks on wood}.
I have also never come across a report online of any GHS fem seeds turning bad on anyone. Some companies, however, have rampant tales of hermies and males. I guess some breeders are better than others at making fems. I would suggest looking up some grow journals that used fem seeds, and finding results by breeder. I did the same thing before I went for it, and I think it is going well. Good luck.
S-Town