From NeoGAF:
How big is the game world?
Around the same size as Skyrim. Source: Bethesda. (Worth noting Skyrim was 3-4 times bigger than Fallout 3).
How many lines of dialogue are in the game?
"Many years of #Fallout4 voice recording complete! Just over 111k lines. More than Fallout 3 and Skyrim combined." Source @BethesdaGameStudios
What are the differences between the console releases?
Both versions run at 1080p and should be identical. They are aiming for a solid 30fps.
Can you change the colour of the HUD?
Yes. Source: screenshots.
lockpicking/hacking minigames are the same as Fallout 3/NV
id and machinegames provided support for the fps stuff
(rumor) The higher the difficulty is you set, the more 'Legendary' enemies you will have in the game, which are harder than normal enemies, but also drop better loot.
No official modding support or Steamworks support at launch. Later in 2016 there will be the modding kit for PC, then Xbox, then PS4. (As per Bethesda).
Skills are gone. When you level up you get a point(s) and you use that point(s) to either:
A-Increase your Base SPECIAL stats (by taking the "Top Perk" in the Perk List)
B-Unlock and Obtain a New Perk that you're eligible to take
C-Rank Up a Perk you already have/unlocked (Do note that some Perk Ranks have Lv Requirements).
Strength
Perception
Endurance
Charisma
Intellect
Agility
Luck
Weapon durability is gone.
In Boston city you can walk inside any building without loading screen. Some buildings have elevators up -- during those rides it silently (and quickly) loads. Source: leaked video.
Dialogue: You only 4 options and they all are very short summaries ("HATE NEWSPAPER") and are categorized (Up option is always a question, left option is always neutral, right option is always negative, and down option is always positive.)