My feelings are, if you're trying to prove to your audience how harsh the real world is, fine, put some swearing in there. If you're like me, I HATE SWEARING, and when you see it in a book, it makes you even more involved in the experience from its impact, whether it's hating what path a character's taking (cursing leads to other things) or shocks you when a character who has been good up till that point in time actually falls down a rung or two (it's traumatizing in real life, even, to hear your little brother cuss you out for the first time, someone you never expected could or had the capacity to

).
I don't know about the rest of the world, but if it's anything like my neck of the woods (Oklahoma), then you can't go anywhere (high-school, college, super-market, church) without hearing "the 'F' Word" at least once. I HEAR IT EVERYDAY

. Then I go to read a book with a Christian message that is trying to show me the harshness of the world, and when I don't see a single curse in there, believe it or not, IT ALIENATES ME. The real world isn't like that. It's great, don't get me wrong, like having quiet time free of "F--- this" or "Screw that," but that sense of a perfect world sometimes defeats the whole purpose of the story. Now, if you can get around the whole cursing thing and make the situation still harsh and true to today's corrupt society, by all means do it (Frank Peretti does a good job of this); otherwise, it just seems - I don't know, untrue.
I hate sugarcoating. I don't do it in my writing, and I try not to do it in my ministry. I feel that someone cursing is just another way for us to counter Satan. There are a lot of good ways to counter people swearing and turning it into a witnessing tool; my greatest strategy is showing people that when they swear they actually don't know what they're saying at all. For example, here's a scare tactic that I learned: anytime anyone ever swore at me by saying, "F--- you," I went into the actual origins of that phrase. Anyone familiar with it? I'd heard it said that it was said often in the Dark Ages, and that whenever anyone said it, it was THEM wanting/doing the F---ing. Corrupt knights who had their way with defenseless women, that sort of thing. That means anyone they cuss out is actually the one that THEY want to - well, you know, do THAT to THEM, which actually defeats the entire point of them putting down a person.
They ALWAYS recoil in disgust. It's just a way for them to see that cussing, in itself, doesn't make any sense, and is in direct contrast with God's ministry, which makes PERFECT sense. The thing with me is, though, I have Moses Syndrome - that is, I usually get tongue-tied - so a lot of the time it works better for me if I get to WRITE that sort of thing down, whether in stories or in sermons.
Anyway...that's how I feel on the subject. In the end, vampires will always scare me (anyone watch FRIGHT NIGHT?

*shivers*)