It seems like different people prefer different communication styles. I don't like IM and I never use them for real-time communication. I'm picking up phone once or twice a day and respond when necessary and that's about it. Similar to e-mail.
I have some folks that I work with on projects that are like this. I'm very much an email or IM guy, since 90% of the discussion is technical. But occasionally I have to work with someone who would rather pick up the phone to respond to my technical question. It's mildly infuriating, since the phone is the wrong medium for that particular conversation, and usually leads to delays even if I do pick up the call to answer the question, because the nature of the conversation doesn't lend itself well to a voice discussion.
And that doesn't even take into account the fact that I'm not going to answer the phone if I'm on another call already, or deep into a technical problem. An IM or email, on the other hand, let's me answer their question without having to totally disengage from my current task.
Obviously these are scenario-specific, and my work environment isn't yours. But things get tricky when our two work environments have to cross...
