Been watching this since the start, and it's pretty good, with one glaring exception.
Big Jim. He has become a standard cardboard cutout figure for "TV bad guy". I hope they write him out of the show permanently, and the earlier the better.
In the book, he was supposed to already be dead by now. We passed that point around the Big Jim hanging scene in Season 1. But also, the dome was supposed to come down too. So, in a way I am glad they stretched it. I wasn't happy about the two-way portal between the inside and outside, but they closed that. Now, the whole Zenith connection adds a lot more to the show which might get bloated.