Ok, more full fledged review:
All the online reviews compare it to CoD, which is fair, because it's obviously running on the same engine. And it's another Nazi killing game, only with the Hellboy Thule society nazi's. And they're retarded. CoD's got that pop and shoot mechanic that's fun, because if you do something stupid, you'll end up dead. Now imagine bumping hero life to 300%... As long as you're one duck press from hiding, you're invincible. Oh, and remember the infinite guards that required you to press forward to take the point? That's gone... you just snipe from cover till they are all dead. It's better than running up on them, since there's a number of occasions where they spawn just around the corner (or worse, all come running out of dead ends you JUST CHECKED), and teleport into their cover animations (at least once THROUGH me)
It's a pretty game, except for the dumb magic powers that cause everything to go all wonky looking. I'm stubborn, but apparently most people spend all their play time in the 'veil' which is gamespeak for 'highlight all the enemies and secrets and hide all the details that aren't gameplay active'. One of the 'powers' this gives you is that you move faster in the veil. I'm pretty sure that's programmer speak for 'drawing fewer textures makes for a better framerate'
This harkens back to the ORIGINAL Wolfenstein game. You're a spy, see. Only enemies have a dumb simple 75deg-ish sight arc and can see your shirt tails flapping in the wind from 300 yards away through a window. So it quickly devolves into run and gun, or as I like to put it 'Hide around a corner and bayonet them as they come looking for you' Which is really more Wolf3d style.
The comparison to Metroid is based on the play style. You run around grabbing crystals and weapons that get you new powers, or books and gold and intelligence that get you (the ability to buy) advanced power abilities. Compare this to the Metroid style of going through an area to get the new powers, while searching for the micro-ups that give you more missles or energy or whatnot. The game even encourages you to go back through old levels (replay) in order to find more stuff. This is disconcerting to the atmosphere. Sure, I'm a spy(they call you that, ad nauseum) sneaking blasting my way into a Nazi base. Intense combat, scary music, horror at the experiments and HOLD ON, I'VE GOT TO SEARCH EVERY CABINET IN THE HOSPITAL HALLWAY WHILE I'M CHASING THE BAD GUY IN ORDER TO MAKE SURE I DON'T MISS ANY GOLD. Your minigames aren't supposed to detract from the main game.
A final note on atmosphere: It's as broken as the fourth Indie movie. The Wolfenstein series is about a guy with BFGs blowing away nazi's and their evil techno-occult creations. Giving the hero magic mainstreams the powers and kinda ruins the whole thing. Even Hellboy didn't get it this wrong, and he's a demon for cryin' out loud.
The upgrade system is solid, and seems properly balanced. It's very BioShock.
They've nailed replayability on the head, with the freeroaming for the first playthrough, but the ability to jump-to-replay specific missions at any time. Especially vital given the collectables everywhere. (Oh, and who doesn't LOVE being able to replay the first mission with all the guns!)
All that said, it's a fun game. You shoot nazis, you get to do free roaming (by free roaming I mean 'wander the city with at most a single alternate path from point A to point B' while fighting off 'random' encounters) You bayonet Nazis (my favorate part by far, and given the bullshit 'magic shield' powers, actually better than bullets). It's not going to revolutionize anything, but if the time between WaW and MW2 is just too long for you, it's a good answer. Anybody else should just get Batman.