Internally managed Exchange? It's not a defacto bad idea, but these guys *will* fuck it up, and generally, untill you get into ~1000+ mailboxes or terabytes of mail, my experience is that it's a waste of money.
Pay someone else ~5 bucks a mailbox and 5gig disk allotment per month, and make them deal with all the management and configuration headaches.
If these guys wanna spend the extra the money and man-hours to do so themselves, it's an option, but the "better deal" for the business-unit side of things is going to be hosted Exchange, by a wide margin.