Apple released iOS 6.1.3 today, patching and closing up the jailbreak. DO NOT UPDATE! They closed the restore window on 6.1.2. This means that if anyone has to restore their device, they are stuck without a jailbreak until another is released. What does this mean for you?
1) If you are already jailbroken, do not update.
2) Do not restore your device. Doing so will force you onto 6.1.3 (exception is older devices that can use redsn0w for restoring older FW).
3) If your device will not boot, before restoring, try holding the volume up button while booting to get into forced safe mode. In this case, you can hopefully get back into your device to fix whatever you did to cause it not to boot.
4) iOS 5 users on iPhone 4s type devices, you lost your chance to update to iOS 6 and jailbreak. Stay on iOS5.