Writers are generally sarcastic, snarky, witty people, and that's wonderful—we tend to like each other like that. But, here's the thing—we shouldn't write for writers. It's kind of like a composer writing a piece specifically to pander to the musicians that see it—it might have sixteenth note runs in the tuba line, but it's probably much more fun to play than it is to listen to.
Sorry. I forgot the point for a second. Any who, I see it a lot—we write characters like ourselves. They're snarky, ironic, and can often times come off as intellectuals—which all kind of adds up to a real asshole, if you don't strike that perfect balance between all the potentially offensive elements.
Do I like sarcastic characters? Yes. Is it just a writer thing? No, but we need to be cautious about it anyway. Take, for instance, the smirk. This is an error a lot of people make—myself included—in the name of vocabulary variety. People tend to think of a smirk as sort of a half-cocked smile which, if that's a universal understanding, it could work. However, for the time being, a smirk is a nasty little bugger, and it makes your smirking character look and seem weaselly.
Take Miranda Priestly from 'The Devil Wears Prada'. While she's a delightful character, she isn't really all that likeable. That's because she's too sharp and kind of nasty. However, Andrea is a great heroine—she's smart, outspoken, but not mean and nasty. It sounds like really dumb advice, but you'd be surprised how often unpleasant characters make it into the hero role, and not even as an anti-hero.
It could be a non-issue, but it's such a dangerous path to tread. The more personable your main characters are, the easier it's going to be for the fans to really connect and care, and those hooks are barbed, making them the perfect tool. Once your reader really gives a crap about the characters you want them to, they're going to care, because ripping those hooks out is going to hurt like a son of a bitch. Of course, if you start ripping them out, making your character slowly transform into an utter asshole—believably, of course—there's going to be a slow pain and an open, bloody wound in your reader, which is kind of our job, right?
But they have to be good people first, or you have to write an anti-hero, which is a whole 'nother beast. The problem is that not everyone likes sarcastic people—though I don't know why—or overly witty people. I feel kind of like a nutter on a street corner at this point, prophesying the doom of your writing career, but that's not what I mean. I'm just saying to be cautious, and honestly ask yourself if your sympathetic characters are actually sympathetic, or if they're just nasty. Honestly answer the question, too.