So, now that the iPhone is gaining proper mobile Exchange support in the form of ActiveSync, I'm hoping that similar happens for Mail/iCal.
While Mail works with Exchange with IMAP on, it's still not a solution that can replace the need for MS solutions fully. Calendaring is the biggest issue, with iCal invites not fully functional when sent to Outlook, and no direct syncing iCal to Exchange. Receiving a calendar invite via Mail is also not quite as seamless as it should be.
I'm just really hoping this whole "Enterprise" thing for the iPhone helps the OS X side too, instead of it being another buzz word Apple likes to throw out and not fully embrace, similar to "Gaming". Yeah, Apple has the consumer market well covered, but some of us would like to be switchers at work too.