OK, first impressions?
I totally thought they were going to play "We'll meet again" at the start of that trailer. Seriously, after listening to hundreds of classic tunes when playing 3 and New Vegas you realise how similar a load of them sound.

Uh, does that house from the trailer have the same layout as the one from Breaking Bad? o.O
Bonus points that they used the same Mr Handy as they did in the original Fallout 3 Trailer. Holy crap is that the same house from that trailer?! XD
Points then:
They've retained some designs from Fallout 3, as in little bits of clutter like the rockets above the baby's crib, the Enclave armour, Captain Cosmos poster, Riot Shotgun from NV. T-51b looks like its had a redesign though (no big wheel on the back). Is that Brotherhood riding those Vertibirds? If so then I take it that Bethesda took a nod from Tactics and brought in the Brotherhood's airships from there (they haven't explicitly made Tactics non-canon, and gave it nods back in 3 too).
It looks a lot greener than 3 did, which is great.
Yay, they had to get Mudcrabs in there somewhere...
Ooh, Super Mutants.

I see a poster on the wall of some slum telling people to "Enlist!".
Eugh, more Red Rocket Gasoline rather than Poseidon for some reason. :/
The city looks a lot more like the original concepts rather than what they went for in 3. As in its more "Metropolis" than just what our world looked like in the 50s with some crap tacked on.
Is that T-45d power armour or a later variant of it? Cool though, a nod to Van Buren where the guys guarding the Vault just before the War were kitted out in the same suits. I'm liking the redesign. It reminds me more of a futuristic car than something that's all edges (which the original design had credit to be, but given that the T-51b's been made to look more advance then the earlier armour can be too).
New weapons on the wall? I see the same laser rifle that one of the guys outside the Vault was carrying (credence to the Kotaku claim that you play as a guy from before the War? Plus the original trailer's house at military crap in one of its rooms the dog passes). A Power Fist maybe. Some smaller laser weapons (not Wattz 1000s unfortunately), and is that a Sniper Rifle?
Pipboy's not been redesigned majorly. It looks more like a bit of military gear, but thankfully they didn't change the original's useless ergonomics (the buttons are all in horrible places, as noted by the guy who originally made the thing, he only discovered this after it was finalised). It has a massive light bulb on the side now however, rather than the light being emitted from its screen (hopefully then it'll be like a directional torch rather than lighting up 360 around you like in 3 and the originals)...
Looks like the family from the start, or in other word's the game's tutorial, don't make it into the Vault in time. ...Or do they?

...Probably. Least the father will.
Overall it looks a lot more realistic than 3 did, but put that down to it being a good couple of years on. Its nice to see the game looking like that though, even Skyrim was a bit off looking. However I'm also getting a RAGE feeling from those post-war towns.