So after 34 hours, my conclusion concerning the engine is that if this is not Gamebryo, then Gamebryo was unfairly criticised for the issues in Fallout 3/NV and Oblivion. Pretty much all the same issues are still present, so presumably whatever proprietary Gamebryo code they stripped out was not responsible. My particular favourite in this new incarnation is that they seem to have ramped up the wacky item physics to a point now where most buildings seem to be perpetually possessed by poltergeist (say that 3 times fast), with dishes and such flying about all over the place every time you enter.
It also seems to me that the new "feature" they announced, namely not zooming in on faces during conversations, was just a cop out to hide their dodgy textures and ropey animations. I'm not sure why it is, but if you ever wanted to make a game full of truly ugly people, then Bethesda would be your go-to studio. Not that we didn't know that already, but what's on show in Skyrim does seem to fly in the face of pre-release claims that characters would be a lot nicer looking this time around. I guess they are better than Oblivion, but that's not exactly a challenge.
Speaking of faces, am I the only one that thinks that it is bizarre to have a FaceGen character creator for the player character in a first-person game where you virtually never (outside of a few combat kill-cam moments) see said character's face? You'd think after they'd expended that much effort that they'd at least give you a few shots during conversations or something. They should just have a HandGen system, seeing as hands are pretty much the only thing of your character you ever see.