MS CRM vs. real Helpdesk System

Hello,
I am preparing to defend my views on not wanting to use MS CRM software as a helpdesk system for my IT dept. I am looking at something more along the lines of Trackit, or something where I can use their tied in software to combine my helpdesk with automated asset tracking, network monitoring and other similar tools.

From what I can find, people say the Helpdesk software available through CRM is basic, and not really good for serious helpdesk applications.

Could I get some of your thoughts as to some of the biggest deficiancies of using CRM for helpdesk that you have found? I am having trouble finding this kind of information on line, so any good links to provide information would be great as well.

Thanks!