As someone who mainly cares about the story, this season is as awful as it can get. I've just finished episode 6. Friends warned me that this season wouldn't have a lot of fighting, but I took that warning less serious than I should have. If you are really in love with Thorfinn, you may find validation in this season by telling yourself "This is all character development. A build up to something great". To those who watch a lot of animes for the fun of it, this season is as boring as it gets.
Story:
The story pretty much takes place years after the events of season 1. Trying not to spoil too much, Thorfinn and a new, somewhat protagonist, guy end up as slaves on a farm. Now add in some farming, screaming, and 10 minutes of torture, and you basically catched up to episode 6 already. Don't expect those happy chemicals in your head to go crazy from great action and heartbreaking drama. Take a cup of coffee and sit ready for some gameplay of Farming Simulator: Trauma Edition.
Characters:
You got Thorfinn and Canute. That's all of the cast from the first season that had a good enough impact on the story for me to remember them. Canute pretty much got an upgrade. Cool guy. Thorfinn has pretty much been downgraded ever since his introduction and he's currently at his lowest point. Sorry if I offend anyone here but he went from happy child to motivated warrior (upgrade) to revengeful idiot to braindead slave. He has no more emotions, the bare minimum of dialogues, and overall become boring. Hence why you can only love this season if you aren't here for the action, but simply for Thorfinn.
For the other characters, you got some new ones. None besides the new somewhat protagonist guy stands out though. You have the kind slave owner.. random woman.. brainless "guards".. somewhat cool guard leader.. and grumpy grandpa. If I forgot any, you can't blame me. Anyways, the new somewhat protagonist guy is your regular boring guy who's just.. living life. He didn't really do anything special besides losing his chill a few times. I'd say the only reason people find this bearable is because the animation and sounds are good and they liked season 1. Comparing the current cast ,including braindead Thorfinn, to the season 1 cast, then this season has become even more of a disappointment. Thors, Thorkell, Askeladd. Nothing in this season compares to their level of coolness (though although I forgot to mention it, Thorkell does have a little screen time here as well).
Anyways, I assume I'll get a lot of hate for this opinion, but I really don't want those action lovers thinking that this season is the same as season 1. The 2 hours you'll spend watching these 6 episodes can be better spent watching half of a short but actually fun series. As I didn't read the manga, I have no idea how long this is going to continue or if it's going to get wayyyyy better, but they will have to get on Attack on Titan's level to make up for such a long character development arc. For real, there are enough animes with a lot of character development that don't even sacrifice 1 episode dedicated to someone's development. Anyways, enjoy it or don't enjoy it, I don't really care.