I can see it is included in the Enterprise License, which I have through the MVP program. So the interest is right now mostly for testing purpose, and learn all the capabilitites of the Enterprise Lic.
I have my own Exchange Server running at home, and thought I might test it. But if I understand correct it is not available yet, or is it just available on demand?
I agree that most companies would probably not want anything installed on Exchange. But it could be a bit different for small companies, i.e. running Small Business Server and just having one server.