There's one sure way for a company to earn the ire of another company, and that's to refer to their products as "irrelevant". Then again, Microsoft and Apple are already poles apart. Lately, a Microsoft's exec gripe with Apple is the iPhone, which he said will not be a good fit for business users. The reason? It's a closed device that will not support Microsoft Office. While Apple certainly has little to no incentive to support Microsoft's software, a good point is made. Many mobiles run Windows and have support for Microsoft applications such as mobile Office, and the majority of mobiles at the very least are open-ended platforms that can be developed for by nearly anyone. That should be important to Apple, because the biggest market for PDAs is at the business and enterprise levels, which Chris Sorenson thinks they will have a tough time entering:

While the entry of the iPhone (with its cut-down version of Mac OS X) into this market offers new options for consumers, Sorenson believes user familiarity with the Windows Mobile interface – and the ease with which companies can buy and develop applications for the platform – will sustain its increasing popularity and help keep the iPhone out of the lucrative corporate market.
Apple isn't commenting. Perhaps Apple's goals are different. Perhaps they don't want to break into the corporate market. Maybe their goal is to convince much more casual or recreational users, like college students or enthusiasts, that a PDA will bring them so much more usefulness than a cell can. After all, supposedly there are already millions of people willing to invest into the expensive device.