the developers can make the setting and situations and characters and story and whatever as bizarre as they want - hell, if New Vegas doesn't have giant molerat mounts and day one DLC featuring molerat armor i'm going to be at least a little disappointed - but a gun is a gun and should feel like a gun.
(i like guns)
i don't really care about overall realism beyond ballistics modeling, honestly. i mean i'm pretty much guaranteed to be playing on "hardcoe" mode (as stupid a name as that is) but that's just because i like CHALLENGE and i'm sure if "casual" mode is anything like Fallout 3 it will stop being challenging like an hour in. i don't care about stuff like thirst or whatever unless it's done in an interesting way (i.e. animations attached to it, so you actually have to STOP AND DRINK and not just assign water to a hotkey and hit it when YOU'RE THIRSTY pops up on the screen in the middle of a fight).