I've converted one iPhone to the new iOS 5 launched a few days ago by Apple.
Unlike the various press reports of disaster, it transferred without incident, albeit taking the best part of two hours.
The phone in question isn't my main one; I preferred to transfer something less critical to check that the various email and calendars (which include Exchange) all worked before I took the plunge with what I consider to be my 'work' device.
It's raised another interesting set of questions about the iCloud transfer, which is a sort of inevitability because the old .mac/.me mobile system is being phased out sometime next year.
It's one of the few times where I need to read the small print before I start moving things though - because some services are no longer supported.
My issue will be with the Apple Macs I still use that are "pre Lion" and non-upgradeable. The main need will be for them to still access email and remain generally synchronised.
I think everything will be ok, but once I've typed 'Yes' into the relevant 'move to iCloud' boxes it looks like a one-way-trip.
Maybe I'll paint the garage doors today instead.