If you have an AT&T account, I recommend updating to 2.0 with itunes. Then when you get the purple screen just restore down to 1.1.4. This will leave the iPhone in DFU. They will try to restore, but the phone won't work because the baseband won't match the firmware version and after 2 attempts give you a new phone. Tell them the phone kept restarting and it showed an itunes logo with a cable. They will think its a corrupted software issue.
I've tried this out with my AT&T 4.9 bl otb downgraded to 3.9bl. They never knew I modded it and won't be able to check since they can't get it out of restore. Enjoy your new iPhone!
