I'm traveling to Chile and considering unlocking my 3G for use with a local SIM. 1. Is there a safe/reliable/reputable unlock solution for the 3G with FW2.1? 2. Besides Visual Voicemail and the ability to use on a different carrier, is there any other difference between a factory and unlocked iPhone? 3. Can I easily revert an unlocked iPhone to the factory state? 4. I only plan on using the foreign SIM for about 3 weeks...do I have to terminate my contract with AT&T? Or can I just put the AT&T SIM back in when I return to the US? Will they even know or will it just look like I didn't use the phone for a few weeks? Thanks.