I finally watched the whole series (so far) and this is my comment for all seasons and episodes:
who writes these [spoiler]shit [/spoiler]?

I liked the history and mythology, until they started twisting it.
I like the battles and the music that goes along. No comments there.
The actors? Come on. Hand-picked for their muscles and their looks. Barely believable. With some exception I won't bother mentioning.
All in all I enjoy watching the show.
What I don't enjoy are the endless scenes of supposed poetic beauty, the pretentious anachronisms, the jumps in story-telling, the twisted timeline, the foretold deaths, the prophecies, the inner turmoils, the silly characterization.... It's poor. It has been all along and no-one seems to know how to fix it.

The biggest burden of the show must be its success. They did stupid things from day one, but people still accepted and followed the show, and instead of using that chance to get better story-telling, they kept re-iterating their teenager targeting plots, as if they were masterpieces.

Nothing was new or original in Season 4. It seems they said all that was to be said, in Seasons 1-3 and then got renewed and went back to the previous seasons trying desperately to dig the stories to bring to life: [spoiler]the same siege, the same brotherly betrayal, Floki's clinging to the past, more betrayals, Harbard, Lagertha's mishaps, child-births and christian woes .. [/spoiler] Nothing original. And they wasted a whole lot of time in utter nonsense, then rushed things in the last episode, then decided to prepare for the next season with what was probably improvisation from Mr.Fimmel [spoiler] as I can imagine anyone writing his speech in paper and getting it approved as a final scene [/spoiler].

All the great scenery and costumes and hairdos and boats... all wasted in the hands of obviously young, overconfident and ignorant writers. If money and ratings is all that counts, then maybe they've succeeded. But if the final product and its filming legacy counts for anything, then they have failed and they did tremendously.
When you can write a summary of an episode in 10 words or less, that's a hollow episode, visually appealing maybe, but not at all profound.

My guess for next Season? Whichever actor/actress is favorite of the viewers and willing to keep the same salary will miraculously be alive. The rest, will be written off in one sentence or less. There will be cameos for the reunion-junkies. [spoiler]Then they will prepare for the Mediterranean [/spoiler]. At least 2 or 3 episodes will be wasted in Kattergat with silly plots introduced in that same season only to be resolved in the next episode. Some events will be foretold, probably in an intense drug-induced frenzy with ominous music. New characters will appear, become prominent, overshadow everything, then die tragically, or not. One good fight mid-season, one in the finale. And in-between the never-aging Ragnar will fight the same inner daemons, restate his bro-mance with the over-played [spoiler] and long dead [/spoiler] Athelstan and try to be the leader he hasn't been since Season 1. Mixed with some Wessex and Paris stories to keep the filming budget under control, we'll conclude the series with endless scenes of everyone saying goodbyes to everyone mostly through long stares and 'don't you die on me' moments...

I'm so disappointed. I hate not being 16 years old, for I cannot enjoy any of that. And I really wanted to.