I didn’t listen to the Burton Group briefing on whether or not the iPhone is “enterprise ready” (apparently Burton thinks not), but I agree with Bob Blakeley’s view as expressed by Phil Windley:
While you can certainly make a case that encrypting data on the device (even contacts) is necessary for many enterprises, the model that keeps apps and data on the Web–removing the need for these to be remotely managed–is exactly the kind of mobile platform enterprises ought to want.
There are applications you can think of–field technicians in areas with poor connectivity who need access to large amounts of data–but those are probably the exception, not the rule. Most road warriors could use Web-based tools with little loss in productivity. I have been amazed at the richness of some of the iPhone applications that I’ve seen and it’s only been a few months.