I personally hate IM in the office, it's akin to waving your hand in front of someone saying "stop what you're doing and listen to me now". I get it in emergency situations but 9 times out of 10 an email would've been more appropriate.
I also hate the "Idiot A is typing a message..." <dum di dum di dum di dum>. In the time it takes them to type (and possibly retype) they could've got off their arse and walked the 10 yards across the office to speak to me (or preferably not bothered me in the first place!!)
Can you tell I've had a bad day/week?