Did it give you a scare first time through? It did for me, but now... I can just rush through the levels without even getting startled.
The old games are great! I've played all possible variants, including:
Doom
Doom 2
Ultimate Doom
Doom TnT
Doom Plutonia
Doom 1 & 2 PSX
Doom 64
Doom 2 masters levels
The Doom series is my favorite FPS game series I've ever played. ^_^