Update: AT&T has told us that an MMS message will be treated like an SMS is today, from which we presume it means that if you buy a 200 message pack, they're essentially interchangeable. However, the language is still a bit vague, so expect more details in the future.

Good news, everyone: it sounds like you can take a (brief) break from throwing darts at AT&T's logo and photos of its various executives. Thanks to a new FAQ from the carrier that focuses on iPhone 3G S and some of iPhone OS 3.0's new features, we have a little more information on what to expect when MMS goes live later this summer.

This AT&T iPhone 3G S FAQ (PDF link) covers various aspects of the iPhone 3G S launch this week, including availability, whether you should pre-order, and how to handle FamilyTalk plan shuffling. AT&T also vaguely confirms that tethering is coming "in the future." But on the second page, it even tosses grumpy iPhone 3G and soon-to-be 3G S owners (remember: the original iPhone can't do MMS for some unknown reason) a bone with this statement:

Later this summer, as part of the 3.0 software, AT&T will make multimedia messaging (MMS) available at no extra cost to customers with a text messaging bundle. [emphasis added]

That's right: once AT&T is ready for all the MMSes that iPhone owners will undoubtedly clog the tubes with, there will be no additional fees—as long as you already have a texting package, which currently start at $5 per month for 200 text messages.

We aren't sure, however, as to whether MMS will be counted differently from regular text messages. For example, O2 in the UK counts each MMS as four SMS messages. AT&T did not respond to Macworld's request for clarification on these points, so we hope the carrier enlightens us all by the time it flips the switch later this summer.

AT&T came under fire last week after Apple unveiled its iPhone 3G S/iPhone 3.0 plans when it became apparent that support for MMS and tethering would not be available when the 3.0 software update arrived this Wednesday. The company has also taken criticism in regards to the upgrade pricing scheme for iPhone 3G S.