We know that Bungie will add tons of decorators and other small atmospheric effects later on. The screens look fine for what they are. You can see how big the environments will be, what the tone and setting looks like and what we can expect from the lighting.
It looks comparable to Gears 2 in these pics, very much in the upper echelon of 360 games (Nowhere close to PS3 exclusives like Uncharted 2 or Killzone 2 of course).
The textures and the geometry will likely stay the same but we can expect a lot of vegetation and random objects to be littered throughout the levels once the game moves closer to completion.
The only thing that really disappoints me is the barren landscape but as I said there are only few decorators like bushes or tall grass in there and the scenes that have them look awesome.
Bungie has a history of releasing early, unpolished screenshots (like
this or
this)that don't do the final game justice. That's the trade off for getting this stuff a year before release.
I'm sure we'll look back to this stuff the same way we look back to the early Halo 2 SP pics.