I like the Companions commenting on your actions and on the locations you visit.
It's cosmetic, but it feels like your progress and achievements are acknowledged.
Yeah that was actually a pretty neat addition. Sure, most of the time they just repeat the usual one-liners over and over but occasionally some little things shine trough. Like Pipes telling you "I'll be right back", spoonfeeding some poor villager her "truth", so he will never again sleep with both eyes closed.
Or super optimistic yet naive Curie asking every scientist or doctor where they studied or if they want to compare notes to help people. Only to be let down every time. Poor uuh girl...
There also seems to be one unique line for every location you visit, plus comments in dialogs (they took notes from FNV it seems).
Cait being able to lockpick for you and NotGarret hacking terminals is a nice touch, but perks are so overabundant that you don't really need it.
But it definitely adds a little bit of replay value.
Except Strong. Strong can rot whereever I dumped him. Unless you kill people and eat them he dislikes everything. I swear he even dislikes me breathing...
I other news:
When I first read the map could be traversed in less than 10 mins I was a little disappointed. But to be honest, the map is so densely packed you don't really notice it. In Skyrim you would spend 5-10 mins just hiking, admiring the scenery and pass by random cave #23. The urge to explore them went towards zero after a few of them, even dragur ruins were always the same stuff.
In FO4 you stumble over so many unique looking locations that I actually fear I break sequence by entering them, since so much effort must be tied to some quest I don't yet have. Quality over quantity. Well, for Beth standards at least.
Funfact: The BoS is now hiring Vertibird pilots! No experience or working eyesight required! Ask for payment up front, since chances that you make it back from your first run are zero.
Seriously, if Beth doesn't make pilots invulnerable unless shot by the player I need a mod for that. If those blind bats don't crash into each other they always get shot out by some random raider. I have seen already 5 birds crashing in 1 hours, considering that the blimp arrived with... 4 (or 8 if they use they use 1 docking station for 2 birds), there must be some secret vertibird plant somewhere I haven't found yet...