Fallout 4 is a beautiful game with some outstanding RPG features!
The engine is one of the most stable, well-optimized, and polished I have had the privilege to play. The new graphics combined with Bethesda's artistic attention to detail create an incredible world to explore, and engaging and very realistic enemies and allies to encounter there.
Something I am perhaps even more impressed with however, coming from a mod author background, is the capabilities of the in-game Workshop features. The ability to break down objects, including entire buildings in your settlement, and construct custom structures and other features, is both well designed and intuitive, and allows a huge amount of personal control over the course of your colony's development.
Take this video for example. This is walking into Sanctuary and touring some customization I did in just the first hour or so of play. The guard station on the left, the military base, the garden, water station, and recreation shack, along with cleanup and various other minor cosmetic tweaks, all were not present at the start. The original ruined buildings and all the junk scattered around were scrapped, and these structures were created "from scratch" using pieces and game drops.
http://www.youtube.com/watch?v=oFr2_rtrjVA
As you build more structures and satisfy the quotas of your city, your city can expand. For example, I constructed a settlement radio beacon outside my military base once my food, water, and bed situation was improved, and new citizens started showing up, which you can assign to various buildings and tasks.
Feel free to post screenshots/videos of your own customization!