Microsoft's mantra up to this point has been "The iPhone will be pretty, but it will suck for business users." Apparently Cingular/AT&T disagrees:

Cingular, which was acquired by AT&T, recently decided that the iPhone will appeal to business users and the operator is now working hard to ensure that its backend enterprise billing and support systems will accommodate the device when it ships, said a source familiar with the company’s plans, who spoke on condition of anonymity.

Gartner's Ken Dulaney is with Microsoft, though, saying the lack of 3rd party support and the lack of a keyboard will make Enterprise customers shy away from the upcoming smartphone. There's also this tidbit:

He suspects that enterprises will likely decide against the iPhone for similar reasons that many decide not to standardize on Mac computers. Even if the iPhone is attractive, like the Mac, they’ll choose BlackBerry or Windows Mobile devices because those have more software application options, he said.

Which spins me right 'round - how's a Mac + Windows Mobile user to feel these days?

Read: Macworld: News: AT&T to target iPhone to enterprise