In terms of the acting and drama, it's a good show, and I made it through a few seasons.
I just always had issues with the historical angle. The real characters of the Transcontinental Railroad story are just too well known if you've spent any time reading Western history.
The "Hell on Wheels" version of the Union Pacific story is a bit like re-telling the story of D-Day with two platoons of boy scouts and an Allied Supreme Commander named Willie Weedwhacker. You just can't tell the story of the greatest industrial enterprise of the 19th century with a core cast smaller than that of "Downton Abbey", and replace all the former (mostly Union) generals and engineers that really built the UP with some fictional ex-Confederate (Only Durant as one of the financiers gets his historical due). May work as drama to a degree if you don't know or don't care about the history, but doesn't compute otherwise.
I finally gave up, even though I really wanted to hang in there until the Swede got killed. (Did he finally?)