I've never really noticed much of it, but it may be because it's mostly British and Japanese series that I watch, plus the odd CSI episode. I'd probably be mildly annoyed at preaching and characters based on that criteria, though I'm pretty good at filtering out a lot of what's coming from the tv.
I must say though that I wouldn't enjoy a character with a habit of restating atheism and trying to enlighten about that. To me it just runs a lot closer to non-committed/non-practising theists who don't really care to educate others in the matter. Outside of these forums it's extremely rare for me to even have to tell people I'm an atheist, let alone bring out argumentation and try to convert them.
edit: I'm more annoyed by having the media depict girls as pink-loving shallow shrieky creatures who want to wear make up at 12 and other stereotypes around the more material sides of society.
