Ever since they changed the IM system, it is virtually a duplicate of the mail system.
Previously, you had the choice to be open to receiving IM's. And if you were, and one came in, you received an audible doorbell ring so that you knew an instant message was in.
Now you receive an IM in a similar way you'd receive Mail. And if you're working in another tab or walk away from your computer, you don't know if someone is trying to contact you. So an Instant Message isn't all that instant.
Yes Mail works. And sure, it could be better organized. I like that the Mail icon highlights and links on a profile when you have a Mail history with that profile.

