Whether I even look at someone's IM status depends on the person I'm messaging. For some people (like a certain guy who is always "Busy" but does nothing but watch anime all day), I'll ignore the status altogether, but for most people I don't know in person, well, I don't don't really message anyone anyway.
And I don't pay much attention to my own IM status, so for anyone hesitating to send me an IM, disregard my status altogether. I change it maybe once a week.