Did a few of the main missions early on, got to the part where you have to find a courser but felt the story was moving on too quick so i stopped and decided to explore a bit and do a few side quests. many hours later, i'm now mid 30's and have barely completed more than a handful of side missions. Thought the game was slightly underwhelming at first because of the huge expectations beforehand, whilst it still is predominantly more of the same, it's still an outstanding game and i'm completely hooked. I just wish the settlement building was more fleshed out, lots more options, proper perimeter walls and an actual reason to bother doing it.
Agree with above about the power armour, i collected about 5/6 sets so far and left a few others but i've used them twice, once at the start and again as part of a mission that basically requires you to use it to deal with the radiation. Found a decent amount of cores i just don't like the view, generally can't be bothered to go and get it and haven't really needed it. Although i'm guessing on the hardest difficulty they are essential.