Several articles have indicated that Apple now has a (small) enterprise sales force, focused on the iPhone and the iPad and, based on remarks by Apple COO Tim Cook, there are seeing some success. Of course, you need to know how to read this type of executive remark. When Cook says that "more than 80 percent of the Fortune 100 are planning or evaluating the iPhone," that means there is at least one (probably at least a few) iPhones in each of those companies -- and a few might have formal projects. I'd guess that quite a few of those iPhone were purchased by individuals with their own money and perhaps reimbursed.
Pardon my skepticism about Apple and the Enterprise. I've been there before. Starting with the announcement of the Macintosh in January 1984, Apple has made a number of attempts to sell to the corporate market. (I know because back in those days I consulted for them about how to sell in the corporate market.)
Apple has always looked to the corporate market as an interesting revenue opportunity, but they have never had a commitment to what is required to sell to and service the Enterprise. In fact, back in the mid-80's when the Macintosh was an interesting and innovative product (if at a smaller scale than the iPhone or the iPad, but , of course, we're talking pre-Internet), Apple even had a corporate council for about 60 large customers. The president of that council once told me that they bought Macs in spite of Apple (he meant their lack of cooperation or support). When more enterprises wanted to join the council (they did get some extra access to Apple), Apple told them it wasn't accepting any more businesses into that group. An interesting tactic, to be sure.
You can't sell to enterprises without understanding how they buy, what their decision cycle looks like (generally long), and what kind of support they will require, both in the decision making process and after the sale. If Apple isn't prepared to put that knowledgeable (Enterprise-knowledgeable, that is) resource into play, then I think, once again, potential Apple customers will find that it's hard to use the Apple products without enough help.
Mitigating my remarks this time around is the existence of an Apple ecosystem which was much thinner in the old days. Now there is AT&T as the service provider (and providing some support) and thousands of application developers. That will help some, but enterprises like vendors whom they can access. They want lots of support and ongoing information about what their vendor plans to do next.
I expect a particular sticking point to be Apple unwillingness to let customers customize the equipment beyond Apple's rules and their generally secretive behavior about sharing futures.
I sit on the sidelines waiting to see how this comes out. If you're an enterprise using or planning to use iPhones and/or iPads in formal projects, I'd love to talk to you.