Crusader Kings 2 update:
I'm thinking of stopping because this Viking experiment is too easy. Me and my Jarls siezed all of England, Scotland, Ireland, the coast of Norway, most of Denmark, Brittany, most of Normandy, and Flanders
Under the leadership of Emperor Hrane "The Sword of Thor", I managed to Reform the Germanic Religion and establish the Fylkirate making my family line heads of the Norse religion. This means I get to change succession laws to ensure an undivided realm. Which means my main character can have lots and lots of babies with no incentive not to have babies. That means a HUGE family and no game-over (the game ends when you run out of heirs).
I know if I wanted to, I could take the rest of the North Sea's coast, cut Roman Catholic moral authority to 0, and take ALL of France within a generation.
The question is do I want to? For you new CK2 players- the Norse factions are harder at first, but if you can seize the holy sites and reform the Norse religion, they are over-powered to the point you miss the simple pleasure of having your mom and hunchback brother seize your county in an uprising because you led your troops to the wrong creek. Or plotting to kill your sister's husband because he wants to provoke a war with the big Empire next door.
With the Vikings you get very little of that fun.