I've locked up many iPhones & have always been able to get to DFU mode & start the restore again.
It's obviously a risk you're going to have to take if you want to experience being jailbroken.
IMO, I don't think you have anything to worry about. DFU restore is almost a sure thing should you get into trouble.
__________________
White iPhone 3GS 32GB
Firmware 3.1.2 jailbroken with Pwnagetool 3.1.4 on my PC running OS X Leopard & Windows 7 Ultimate!
|