I'm not sure I agree with some of what you say Zylon... yes the latest game pushes the boundries of hardware right now, but if it didn't then where would the game be? At its most basic its an FPS first and foremost. And an FPS that doesn't look as good as others, doesn't make full use of hardware available? Well thats not going to inspire anyone. It needs to push the envelope if it's going to get noticed and sell on more than the name alone.
You've not fought the enemies in the game (I presume). These things take a lot of shots to drop. Zombies keep getting back up to attack you - one shotgun shot to the head won't do it at this stage. Imagine 10+ of them, you'd be swamped. Attacks on mass are out - claustrophobic, dark and scary settings with things that actually take effort to kill are in.
The whole concept here seems to be moving away from running in all guns blazing, one man army style play. You are not Rambo. You're a lone marine trapped on a planet which is steadily being overrun by the forces of Hell, and eventually you have to go to the source to fight them. It works much better this way in my opinion, the idea that there are hundreds of zombies wandering around seems a little unrealistic to me - a lot of people died in the initial attack, and many of the zombies have been eaten anyway (one of the cut-scenes shows a hell-hound eating a zombie).
Suffice to say, this is not a Serious Sam game. This is all about fear, and it looks like it'll work.