EA's space-horror game isn't as scary as you'd imagine, but it is very well crafted as a shooter.
It's clear that Dead Space wants to be scary. It has the right trappings, from the lost-on-a-spaceship concept to the limited health and ammo pickups, the audio and video logs you find (which feature allies screaming at you), and the blood-splattered environments and occasional disgusting enemies. But it seems like -- in a few too many cases -- the designers chose to hold you by the hand and make something look cool instead of making it look scary. When you're upgrading your suit (which itself makes you look more like a game's boss than an everyman), using Stasis to freeze enemies, picking up explosive canisters with the equivalent of a gravity gun, and purchasing weapons that dissect enemies in different ways, you don't exactly feel vulnerable. Mix in more than enough checkpoints and the ability to draw a line in front of you telling you where to go (with the touch of a button) and it's easy to settle in and let the training wheels take care of you.
Assuming you weren't misled into expecting something along the lines of Silent Hill, however, I don't think you'll be disappointed. Dead Space tries to have things both ways by being scary and offering plenty of gunplay, but it's well crafted throughout. I remember debates about whether Resident Evil 4 was as scary as previous Resident Evil games, and the consensus was that no, it wasn't -- but it was better designed, so who cares?
A better description of Dead Space is "a limited-ammo shooter." You spend a lot of time moving through corridors and taking out a few enemies at a time, but the game gets difficult (and really good) when it locks you in a room and forces you to kill everything before moving on. When that happens, you have to use strategies such as freezing a few enemies at a time...and then punching their frozen bodies just to save ammo.
The much-hyped dismemberment system plays into these strategies as well, since you can shoot off enemy legs to slow them to a (literal) crawl or slice off an explosive flesh bag attached to an enemy's arm and then use the gravity gun to fire the bag at a whole batch of foes. It works incredibly well when mixed with the limited-ammo concept, as you can almost always find a way to kill an enemy more effectively than just firing quickly -- which helps keep the combat interesting during the routine corridor sections of the game.
Despite the combat, I still found a few too many similar-looking corridors -- the game is long enough (I clocked in at about 12 hours), but it's pretty much the same thing all the way through, with a few minor minigames, puzzles, and zero-gravity segments (where you go outside the ship and jump from floor to ceiling with gravity boots) sprinkled in. Find a key, unlock a door, move on to the next locked door...then enter a room where you have to kill a bunch of enemies and fight an occasional boss.
Dead Space is at its best when it does things unique to the third-person shooter genre; the aforementioned zero-gravity sequences (which feature fantastic audio effects that make you feel like you're in outer space), the storytelling method (events unfold via hovering video log monitors that you watch as you walk around, rather than through traditional cut-scenes -- and it's much more impressive than the events themselves), and the dismemberment system all come to mind. Apart from the lack of variety within them, the characters and environments are some of the best looking on the market, with blood splatters and rusted metals all over the place.
Dead Space ultimately feels like an incredibly polished and varied 6-hour game stretched out to make it twice that long. While I felt like I was repeating the same objectives a few too many times, the combat held up so well that I didn't even mind...too much.