Just finished the first season. This is a really good show. Definitely worth the watch. It develops at a really good pace. Good writing and acting. I like Vikings as well (similar, but VERY different shows). Last Kingdon just focuses on the raids of Wessex, and focuses more on the Saxons. Looking forward to season 2 (whenever it is released).
Watched the first two seasons, and now I am going to take a break.
I highly recommend the Last Kingdom to anyone that is into historical shows. I thought the plot for the second season was really smart and credible. The characters make tough decisions with imperfect information, and the show highlights how difficult it is determining facts in a society where memory is the only record. The show keeps the focus fairly narrow, which makes it more interesting and more tense in some ways. Loyalty is so transactional in that world, and so much of survival was just luck.
The acting is just OK, and the lead characters get really lucky, a lot, but those issues are more amusing foibles than problems.