Assuming it's 2-cour, we're not getting to Farmland Saga, so the 'worst' part of the manga (at the very least, certainly the slowest part) won't be adapted. We might not even get to Askeladd's resolution.
My biggest fear is how they handle Thors and Askeladd. It's a shame that they won't be able to get to Thorfinn's character development.
Also I sure hope the fights look cool and they don't try to skip over the purposeful values dissonance the author invokes.