NO SPOILERS----Just Finished Season 4 of Man in the High Castle. Like most 4 season shows, it had it ebbs and flows but I enjoyed it throughout. Arguably, one of the first shows to put Amazon Prime on the map. As such, it held better than most 4 or more season cable shows IMHO.
NO SPOILERS----The ending is fairly tidy. Having said that, they knew when they were writing S4 that it was going to be the last season so one would expect such a result.