When all of the expansions are in place, Crusader Kings II will be a completely inaccurate title. They'll just have to change the name to 'Medieval Chaps and Ladies (also infants)' because everyone will be playable, even if they have no interested in Papal-dictated conquest or monarchical pursuits. Moving away from the previous alternate history DLC, The Republic is a meatier expansion that should alter the game significantly. Money, not blood, drives the engine of the merchant republics. Venice, Genoa, Pisa, the Hanseatic League and Gotland will all be playable, and Patrician families will have a greater emphasis on trade, cash and political corruption, the latter of which isn't quite the same as defenestrating your first born. Probably.
The Republic opens for business early 2013 and will cost $10.
Leonard Nimoy would like to tell you about Venice's history now, if you don't mind.