Do you know what really grinds my gears? "lol". I mean, what's up with that? When was the last time that you heard a funny joke (in person) and just blurted out "LAUGH OUT LOUD"? I thought so. It is SOOO lame.
Besides, if the point of an messenger abbreviation is to be able to type faster, than the word "haha", as in the noise someone makes when they ACTUALLY laugh, is only one letter more. And if the joke is particulary funny you can lengthen it i.e.: hahahahahahaha. "lol" cannot be modified.
In summary "ha-ha" is an acceptable word, "lol" is not. Please do the English language a favor and stop using it.