What happens if...

.... the iPhone OS freezes and you need to reboot? Usually it's a case of removing the battery and majority of the time the freeze is not down to the OS but because of the network it's using (just ilke when your router stops talking to the internet as your ADSL has locked it up with static or such like and it needs rebooting).

@Ian, Windows Mobile 6 is excellent and streets ahead of WM5, I have just upgraded my HTC device with it, runs so much faster, more stable and from what I can tell someone is porting the "Touch" software for other HTC devices, al a iPhone style interaction.