I think emoticons are almost entirely a useless entity. If you like them, I mean, no judgment (maybe a little judgment. I'm just being honest). But really, it's your personal choice. Here's what I think it comes down to: I passed a copious amount of notes in my middle/high school career, and undoubtedly I was all about the :), ;), :p. You name it, I used it in excess. I think I just peaked early where the smiley is concerned. But really, to each his own. Use emoticons all you like. I won't de-friend you on Facebook over it or anything.
There is one exception to the rule though - one instance in which I am extraordinarily thankful for that little two (or three, depending on your preference) character magic trick: when they act as a buffer. It's very useful in any situation wherein your tone can't be read. A well-placed emoticon can be the perfect safeguard alongside saying something that is potentially a little bit questionable. So if I'm saying something that COULD be interpreted as offensive (but of course I don't mean it to be), maybe I add a little smiley guy to diffuse potential reactions. Not sure someone will pick up on your sarcasm? Wink that sucker. As a person who can barely go six seconds without saying something smart-alecky, I have to be honest, I require a lot of emoticon buffers. [This is not to be confused with the person who actually says something offensive or hateful and then adds a smiley so it looks like a joke but everyone knows it's really fully true. I'm not trying to rationalize an intentional jab, just a harmless sarcastic comment. To recap: the emoticon buffers sarcasm, not being a big jerk.] So I soften the blow of my brilliant wit with the occasional emoticon. I may have said something iffy, sure, but hello, I added a smiley face. So, what? You're going to get mad at me? How could you have possibly misread that... I used a smiley face. There's nothing confusing happening here.
I could just stop being so sarcastic. But probably I won't. So in the meantime I will continue to use emoticons as my life and humor necessitate. And likely shun them at all other times.