I think it sounds just a little disrespectful when used with a stranger.
Also, please don't use textspeak abbreviations here. That can get you in trouble with a moderator. (By the way, this is the only board I've ever been on where I've seen those two abbreviations, but I see them a lot here.)
That sounds right, Canb3rk. Remember, though, that some people might think it sounds a little rude. If I were you, I'd avoid it when I was trying to be polite. It's fine to say that to your friends or in other casual situations.