For me the game is an improvement over F3 and NW in many ways, just the dialogue and skill progression is really bad. One thing that I think is pretty cool "immersion" wise is that Brotherhood of Steel will often send out helicopters with troops to attack Super Mutant camps, and for once raiders actually occupy a large portion of the areas around the cities, not just some random raiders in an abandoned house located miles from other settlements. Wish there were more trading caravans, I have yet to see no traveling caravans, just the occasional trader and dogseller.
Weapons also doesn't appear unless you're holding them, gotta wait for a mod that actually displays the weapon on the back or the hip. And darker nights. I also wonder if you at some point can become a Super Mutant yourself or if the mutant armor you pick up is designed for a potential follower. Also, the default keys are horrible, no idea why they decided to change the control layout from the other games, had to remap and some of the keys I wanted to change wasn't even displayed in the control options.