The iPhone's support for Microsoft's dominant email and calendaring Exchange platform is an essential part of iOS's appeal to business users. Integrating MS's ActiveSync mobile device connectivity into Apple's gear, which started back with iPhone OS 2.0 in 2008, helped make the upstart smartphone into a viable alternative to the dominant BlackBerry ecosystem (and look how that worked out).
Update: See Thursday's post for more firsthand information on how Exchange and iOS have a history of not playing nicely.
Unfortunately, ActiveSync has always been a mite quirky on iOS. While the core email sending and receiving functionality usually does as it should (with sustained support for push email a sometime exception), calendaring doesn't always fare as well. Delegation of calendar rights, access to third-party calendars and meeting invitation handling are among the sore spots that may cause issues for power users.
It now looks like iOS 6 may be exacerbating some of these challenges. MacRumors highlights an internal memo from a "very large company" asking employees specifically not to upgrade their devices, as there may be some situations where declining a meeting invitation inadvertently sends a full cancellation notice to all the other attendees. In fact, I've seen this behavior before, only very rarely -- it came up once or twice on both iOS 5.1 and from iCal under OS X Lion over the course of a few months, while working with Exchange 2007 meeting invites -- but the current instantiation seems to be easier to trigger. Meetings with large numbers of attendees may be more problematic, and/or meetings where the organizer and the recipient are not part of the same Exchange organization.
What can make this sort of issue more frustrating for both IT and device users is that these issues are usually intermittent, hard to reproduce and may hinge on very particular combinations of circumstances and Exchange microversions. There's a reason Microsoft sells expensive service and support contracts with its infrastructure products, and also plenty of reasons why hosted Exchange and alternatives like Google Apps are gaining ground on traditional in-house installations.
You may be eager to try out the latest and greatest version of iOS, but if you're depending on your company's IT department to support your connectivity to the enterprise calendar system (to say nothing of VPN, file services, email and all the rest) then please do yourself a solid and check with your local gaggle of geeks before you upgrade -- not afterward.