It has just come to light that the UIDevice uniqueIdentifier property is deprecated in iOS 5 and above. No alternative method or property appears to be available or forthcoming.
Many of our existing apps are tightly dependent on this property for uniquely identifying a particular device. Can anyone suggest any ideas how we might handle this problem going forward?
The suggestion from the documentation is...
Do not use the uniqueIdentifier property. To create a unique identifier specific to your app, you can call the CFUUIDCreate function to create a UUID, and write it to the defaults database using the NSUserDefaults class.
... however this value won't be the same if a user uninstalls and re-installs the app.