Playing as VikingsLo there I see my father...
Hell yeah. Playing as a Norse is so much fun. All the raiding, pillaging and invading is enjoyable. At least to the point where it gets hilariously easy when you get around 2000 Gold + 2000 Prestige in one go by raiding Italy including Rome and Venice, Greece, Constantinopel, and even the yet to be Holy Lands. Maxing out all of your counties even those that you don't own while steamrolling Europe with your pagan single-border casus belli will give you plenty of hours of joy.
Buuuut. After that it really gets quite lame. The raiding becomes repetetive (who knew) and the inability of the AI to defend itself makes it even worse. There really won't be much of a challenge as the Christian states are highly unlikely to declare a holy war on you and even if they do you destroy them with ease.
I do recommend The Old Gods when you want to play as a Viking.
Playing as England
If you want to learn the basic game mechanics I can recommend playing as an Irish ruler. You can raid but wont be in imminent danger of being wiped out immediately.
Unlike when you play as Wessex.
And oh my god that is a nightmare. Having 20k Vikings right at your doorstep is quite intimidating when you command a maximum of 5k men into battle. The only way I managed to beat them was by hiring mercenaries with the money I earned from my marriage and joining forces with my allied Britains. And holy balls. I won.
Aaaaand hello Denmark Invasion! Here, friend. Take another 20k Vikings on a conquest to steamroll your lands! ♥♥♥♥♥♥♥♥.
Don't believe the DLC description stating that you can "defend your lands against the invading heathens". You will be very disappointed.