Have recently picked up Fallout 4. It's a game I've wanted to play for some time, as I've played the series from the start. Fallout 4 has much better shooting mechanics, pretty much in line with a contemporary FPS game, something I felt that Fallout 3 and NV were quite clumsy in handling. While the basic plot, a search for a missing family member, is well worn, there are enough deft, imaginative touches in world-building and character development, and plenty of micro narratives in various locations, to make the story fairly engaging.
The main thing I was worried about was the simplification of the character system. There are no longer discrete skills, but rather, these are tied into stats and perks. Being a fan of old school RPGs I would prefer separate skills, but overall, I felt the new system worked. Another major point of contention seems to be the lack of choice in quest outcome. Again, while it does push the series further away from its RPG roots, it didn't bother me as much as I thought it would, perhaps because I usually play a "good" character anyway.
Overall, I'm really, really enjoying Fallout 4, to the extent that I'm not bothered by the aspects of the game that are not entirely to my taste, and willing to enjoy the series' transition to open world shooter/RPG lite.