(first post from old lurker of /. here goes, pardon my language by the way. im not too articulate in english. i'll try to avoid the brainfarts though, heh.)
i dont find anything scary on BOO!-tactics. Sure, they might give you a good jump or few, but in the long run they do nothing. Doom had a good start, but after you learned to empty a clip to the general direction behind you every time you heard a strange sound, the fright-aspect disappeared.
That is exactly why i love Silent Hill -serie. To me, the basic idea of the serie is to scare you with what you don't understand. Take for example the first set of monsters you meet in SH2, you had no idea what they were but you knew you're not going to survive if you didnt run or start smashing uglies with whatever you could find.