Great expansion. Adds heaps of new elements to the game and I love the fact you can play a 6 player game now.
This expansion adds a number of new modules that can be added to the game. It would be useful to go through them but to be honest the only one you'll be likely to care about is the extra player, which is almost worth the price of the (too large) box.
The other modules are interesting, but how often are you really going to play this outside of a somewhat inebriated setting? When you play it that way (the best way), all the extra rules designed to get around people gaming the system just are not all that relevant.
So if you need the extra bag and black nun? Well worth the purchase. If you are just looking for a bit more complexity to your Sheriff of Nottingham experience? I'd say the time and money is better spent on something a bit more meaty.