As with the consumer iPhone plans, two-year commitments and voice and data plans are still mandatory. You can now pony up $45 per month to get unlimited data, visual voicemail and a stingy 200 text messages. Bumping the plan up to $55 gives you 1,500 text messages. For $65, you get all-you-can-eat everything. That's Internet, messages, data, etc.
For the international traveler, shelling out an extra $25 per month on top of your existing data plan gets you 20 megabytes of overseas roaming in about 30 different companies where AT&T has roaming agreements. If you care to spend another $60 per month, your overseas roaming limit jumps to 50 megabytes. If you surpass that amount while roaming abroad, you'll be charged by the kilobyte. (This would never work for me, I use hundreds of megabytes of wireless data per month.)
If you've been holding off on updating your corporate phone because you wanted an iPhone and it wasn't sold by AT&T via its enterprise channels, this is good news.
I guess the iPhone's pending compatibility with IBM's Lotus Notes is supposed to make up for the fact that the iPhone doesn't support Exchange. If that doesn't work for your enterprise, there's always Windows Mobile and BlackBerry devices. For the rest of the world...