Feudal politics are fun in and of themselves, but it's actually quite educational to see how well these kingdoms and empires could be run by a feudal system.
Whether you dig the idea of breeding the perfect king or simply acquiring as much land as possible through sneaky, underhanded ventures, this is the game for you.
Not so much bad as inconsistent. For example, in order to create a Count, you do it from the kingdom status screen. However, to add to that Count's land or to make him a Duke, you need to find him on the map. Also, after loading a savegame, you MUST remember what nation you were playing before because you have the opportunity to choose from any still in the game. This is more difficult than it sounds, since my Count of Parma became Duke of Karnten by heredity and King of Venice by conquest, and I don't save my games by their default descriptive names.
Crusader Kings ran unexpectedly slowly at times. Perhaps it's the AI and familial calculations but often there's not much visibly going on while the game slows.
The Crusades are poorly implemented, the Pope, oddly enough, doesn't excommunicate you for taking his Papal States away in war, and it takes a very long time to find a good match for marriage, be it for stats or inheritance.