If Apple could make it so it has an awesome setup to administer it, then I would love it.
Imagine having mobileme functionality, but it all running on your own private servers.
-Find my iPhone listing all the iPhones in the company.
-Real iCal syncing for everyone.
-An awesome Web interface, along with push email for iPhones/iPads
-One piece of setup for the users' data on their macs
-Good presence indication for users
-Making iDisk work a little more like Dropbox, or even a step further, turn iDisk on for certain folders and it does the work for you.
-Notes, Todo and Task syncing
-The ability to push in house or corporately approved apps to iPhones
All without MS Exchange, would be a real game changer.
I think Apple would do really well to pitch this to businesses as a real competitor to RIM's BES. Especially after what is happening with Saudi Arabia and UAE. None of your corporate data should be accessible by a third party, including RIM. If you are the only people hosting those services, then that will be true.