If you have an iPhone 4 and have been counting the days until a carrier unlock was available today is the big day. The ultrasnow carrier unlock can be downloaded with now.
The unlock works for the iPhone 4 baseband 01.59 and 3G/3GS basebands 04.26.08, 05.11.07, 05.12.01 and 05.13.04. Once unlocked, you can port your device to another compatible network.
I wonder if now that jailbreaking is covered in the DMCA as fair use if there will still be the fight between the unlock writers and Apple with the break/fix cycle. As Apple pointed out, you will lose your warranty if you do this.