It's good if you're looking for some gems out of the old fandoms.
Although if you're looking for more of the explicit content, there's always archiveofourown.org which has a much more user friendly layout. But older fandoms don't get as many hits there.
Although now I see what someone meant when they said ff.net is where fanfiction goes to die. Getting general feedback from readers (ie. reviews) is like pulling teeth. Personally, I only use ff.net to reread some past favorites that originally gave me inspiration.