^^ It's definitely one of the most accurate shows on T.V but there are definitely faults.
Firstly, the political system is very wrong, it appears that Jarl Haraldson is almost a dictator when it comes to his control, however in a viking society any free man had a say and was able to freely oppose the Jarl without consequence. Secondly, the show makes it look like the first time the vikings raid England (though I think it might have had a different name back then), that it was the first time they discovered it. I'm pretty sure they had knowledge of England a couple of centuries before the raids started to begin.
Whilst these might seem like I'm knitpicking, they're both bretty central to the plot of the first season.