Okay, I'll break down my impressions from the first hour:
+Graphics are really good; lots of moving shadows, steam, fog, and so on.
+Sound design is superb; music is muted for the most part, then goes insane when enemies appear: lots of little sound effects
+Mood, mood, mood.
+Severing limbs is cool.
+Very high creep factor; enemies bust out of air vents, lights flicker, things clatter and clang in the distance.
+Your character is an intergalactic mechanic.
+Voice work is good, rarely gets in the way of the mood.
+Backtracking is present but light, so far.
+Stasis nodes and telekinesis are cool, though there are only a few simple puzzles in the first hour.
-Sometimes sluggish tank controls; could use quick 180.
-Some shadows are jagged and aliased.
-Zero-g combat is a bit awkward.
*Story told through in-game conversations over radio and scattered audio logs.
*Enemies can climb up walls.
*Sounds in the vacuum areas are properly muted, except for the main character's breathing.
*Suits and weapons are all upgradable using power nodes.
*I died once after being surprised by a new enemy.
*Lots of blood and gore.
*Dialog is light for the most part. Usually 5-10 minutes between talking segments.
*After the first ten minutes, you're completely alone. The other members of the team [that are still alive] are elsewhere.
Really, really good game so far.