This is nice bonus for those of use who like to travel around the world and need access to foreign SIM cards! Hopefully, this will be extended to all devices and not just the iPhone.
I do wonder if Apple's decision to include world enabled GSM in all phones plays a role here. Verizon is more than happy to unlock the SIM card in your Verizon iPhone for travel abroad. There had to have been pressure, or some observed decrease in sales/ increased turnover that prompted this.