Sorry, but not according to Verizon's Customer Service. Not only have I been charged data usage for using Mobile IM (not just the initial download, either) but when I questioned it - as it's no where on the MOBILE IM section or FAQs - they pointed to this in the 'Customer Agreement'
"Additional features and services such as operator or directory assistance, call dialing, calling card use, Call Forwarding, data calls, automatic call delivery, Voice Mail, Text Messaging and wireless Internet access, may have additional charges. Features such as Call Waiting, Call Forwarding or 3–Way Calling involve multiple calls and multiple charges."
which says nothing explicitly about getting data charges or using the internet for AIM. Infact, the MOBILE IM section on this site explicitly says there are no charges other than being billed as TXT messages. CSR claims Mobile AIM requires you to use the internet, which incurs data charges.
It most certainly is...because that section from the Customer Agreement that I quoted really doesn't justify these charges or state, even ambiguously, that Mobile IM incurs data charges.
[keep it relevant]