AT&T - MMS/Upgrade Eligibility
As for upgrade eligibility look here (my 1st post, so you'll have to reconstruct the URL :-X)
wireless.att. com/ learn /why/ upgrade-advantage.jsp
As for MMS, on a wireless account, when adding an iPhone Data + Voicemail feature, it adds an MMS Opt-Out feature as well which as you can guess, blocks MMS completely. As to why this is, I am not sure, because yes the iPhone doesn't support MMS, but there might be the chance that the iPhone text plans (at least the old SOC codes) didn't include MMS and would charge you if you received one, and in order to avoid people being charged for MMS they couldn't even get, they would block it instead. As for it being a "Manual" process, that just means a person "Manually" starts the account sweep and checkups are done by the sweep teams to make sure all the features have been removed, it is NOT a customer by customer process. As I remember, it took about 2 weeks to change the old 7-7 Early Nights and Weekends features from $7/$14 to $8.99/$16.99, so I expect roughly the same time frame for this switch. Its not that big of a deal, you've made it 2 years without it, what's 2 months?