It may not seem like its ultra complicated, I would add an ability to switch dictionaries if I were smart enough to make FF add ons. (EFF also has a short list too, not a big deal as the long list is better in my opinion).

dice or RNG? Some say dice is the best form of randomness, regardless, this add on will still give password crackers a run for their money, which is the reason why we want to use passphrases over passwords.

This app is fine just as is. Props to the author and EFF for this solid work.