I got pretty far on my first attempt to beat Doom 3. Maybe even 75% through. That leaves a good many hours left, though, as according to Steam it took me 13 hours to complete the game on this try. Which I think is too much with such monotonous gameplay. F.E.A.R. had the same problem.
Doom 3 is the only game I've seen so far to have a mirror scare. And one of the few to have mirrors at all. Deus Ex had mirrors, as well Mass Effect 3 in the bathroom of Normandy's captain cabin. I guess it's an engine limitation or maybe reluctance to allocate resources to implement such a feature. But you'd think that mirrors would really add something to horror games like F.E.A.R. and Dead Space.
I installed a duct tape mod for the run to counter a bit the darkness of the game. It attaches a smaller version of the flashlight to the shotgun and machine gun. It prevented some of the surprises, and as well made the stupid, complete darkness bits more bearable. I wonder what they were thinking with that. It's more of an annoyance than a way to build up tension to not be able see enemies.
What I didn't remember of Doom 3, was how lame all the guns in the game feel. Or maybe I didn't have much to compare them to back then. Still, the sound effects are simply feeble. There's very little weight behind the guns. I guess having more recoil would've helped too. Even Deus Ex: Invisible War's -- that came out a year before Doom 3 -- guns felt better with how the shotgun and sniper rifle ragdolled the enemies.
I played through the expansion, Resurrection of Evil, as well. It's the standard deal; more of the same stuff with few new additions. And it has half the length of the main game, which really makes it a tighter-packed, better experience. Also, Jennifer Hale as McNeil in RoE felt quite out of place. Her voice didn't fit the doctor at all.