We are also using Meebo to IM a librarian, and it has been a popular service. We haven't done much formal marketing of it, but it's on our home page, which makes it easy to see, and we demonstrate it at inductions (and I think it makes an impression). We recently did a survey of the students about our services, and the chat service was praised quite highly.
In the future, I'd like to do more formal marketing and perhaps partner with other libraries to expand our hours (right now, we are only available to IM during our staffed hours, 9-6).
There tends to be good use of chat services if the service is easy to find, is open during times when students need it and students get a fast and satisfying service (and thus do word-of-mouth marketing).
A really interesting OCLC study about the success of chat services called 'Seeking Synchronicity' came out last summer and is availble here:
That study has been influential for us and has helped us to better structure our service. I'm happy to discuss any of this further, if you'd like.
With best wishes,
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