I find them annoying and they make me picture the poster as an idiotic 12-year-old (a 12-year-old who happens to be an idiot, that is). I don't know why. Still, I do get their point:
Avaholic03 said:
In normal face-to-face conversation, more than half of the information conveyed is non-verbal.
If I remember correctly that's actually 90%. 90% of the information you are trying to convey is lost in pure text form. Isn't that nice?
brunothepig said:
They can be used to express emotion or tone, a lot better than any other method I can think of in text based communication. [...]
After all, which seems like a stranger response to, say, my girlfriend informing me she can come visit me this weekend? "I am happy" or "

".
Emoticons may be more convenient, but if you are even a bit eloquent you shouldn't have any problems with not using them. You could say something like "Now I'm really looking forward to this weekend." I mean, I am terribly lazy and still don't use emoticons. They are never necessary, they just make things easier. And look stupid. Well, most of them, anyway.
Having said that, I wish there was a better (and convenient) indicator for the use of sarcasm.