The Settlement system is a great addition, allows players to add custom building and homes for not just random NPC's named "Settler" but player owned by not setting up a beacon. My first game I found red Rocket and turned it into a player home. moved all workbenches to the garage so I had a central crafting area, put storage containers in the area with the HAM radio, turned the office into a bedroom. Since I didn't add a beacon it was never attacked and storage was safe. That was a good thing compared to having to buy a home and then choose predefined furniture layouts like past games. I have used the same site for the next 4 finished games for the various factions and am now working on my fifth game siding with the minutemen for the game conclusion.
Then the actual settlements adds a whole new game dynamic that can keep someone busy for days on end just perfecting individual settlements. Replace vendor stations with new ones, add a few lights, give settlers better gear... One can lose themselves in fixing settlements to be their best. There's tons of stuff that can be done and each settlement location is unique making the player have to think about how a new building is placed to maximize the space allotted.
Dialogue in general is an improvement over past games, I have yet to hear a guard repeat the same lines another guard says for the umpteenth time... Arrow to knee comes to mind. This is refreshing compared to past games when you know what random NPC #245839 will say, though the raiders seem to repeat lines but really only noticeable in sneak mode so isn't a huge deal breaker.
Use of teddy bears and skeletons as decorations needs some praise, whoever was making interiors and made creepy skeleton baby in the pram with a bottle in its mouth having a small body and an advlt sized head... Or the skeleton kissing a skull in a urinal... or the teddies playing checkers... or the teddy in the rowboat behind a file cabinet... I could go on for days about the oddities I have spotted that are either skeletons or teddies. I love them all even if many creep me out. Little details of that nature is something I expect from Bethesda and FO4 did not fail to deliver!
No forcegreet quest givers in Fallout 4! Yay!!!1!1! sadly the quests just randomly pop up but that's still 1 gazillion times better than a forcegreet. you can ignore the quest given and that's always better than being stopped as you run along to talk to a quest giver you never wanted to talk to, to begin with. Suggestion... don't automatically add the quests either. BOS is easy enough to find without having the radio signal force it upon you... there's gunfire and all that happening drawing the player in. As for the Railroad start... instead make it a topic to discuss with NPC's to get the quest, make one named NPC who is a part of the railroad and have him/her be the main quest giver.
Love the random notes that give side quests. More needed lol! That's a good Bethesda trait right there, random note found adds a quest that's just for fun to do. Makes no major difference to the endgame and doesn't always provide a benefit to the player to do but is a good fun addition.
All in all maybe Bethesda deserved more GOTY awards for FO4.