Apple has finally patched the gaping lockscreen hole in iOS 6.1, but in the process it's also killed-off the exploits used by Evad3rs for their Evasi0n jailbreak. In fact, Cupertino went as far as to credit the jailbreakers for finding the four of the six holes. If you're running a jailbroken iPhone or iPad, don't update, for now.
Unfortunately for all those who used and loved the stupidly easy to use Evasi0n jailbreak, you'll lose it if you update. In fact, only a tethered jailbreak for older iPhones and iPads has been released for the time being, and tethered jailbreaks are a pain in the arse.
Hopefully other exploits will be found, but something tells me that's going to take forever, if it happens at all. So, you currently have a choice. Seal up your iPhone's lockscreen with the update and make sure some nefarious character can't break through your passcode with a few simple, well-timed button presses, or stay jailbroken. For me, the choice is easy. Don't update and keep an iron-clad grip on my phone. [Apple via Ubergizmo]