Gameplay was fine, if unoriginal. The dismemberment mechanic was a refreshing change from the tired old 'insta-kill headshot, anywhere else and they don't even notice'. Zero gravity was fun and well executed, particularly in the 'tumbledryer' boss fight, plus it was the 1st ever game in which I'd heard, or more appropriately, not heard, the effects of a vacuum so realistically implemented; you could still hear Isaac grunt loud and clear but anything happening outside his helmet was considerably muffled.
Unfortunately, as a horror game, It only ever startled me and that was only when those play dead monsters jumped up when I got close and even then, it was less effective than my sister sneaking up behind me and poking me in the ribs. The scariest it ever got was when I met my first monster and had to run for dear life. Then I picked up my first weapon - which also somehow imbued me with the powers of Arm Flailing and Foot Stomping - and from then on, I was just casually strolling from room to room, redecorating the walls with zombie innards and selling my excess ammo.
The main character was just a dumb, grunting drone who was about as sympathetic as a paving slab - yes, even when he puts his hand on his helmet at the end as if to say "grief simulation active"!
Plotwise, everything the game was having me do seemed utterly pointless because the ship was fucked, the crew all either dead or zombified and it's orbit decaying so when I asked myself what I would do in this situation, the answer was always "Set the self-destruct and get the fuck out!".
It kept my interest long enough for me to finish it once, didn't play it again.