The Dev Team has struck again, negating the security work of the iPhone 3.1.2 update. Looks like it'll work even if you've never jailbroken your phone before (though soon-to-be-released hardware may not?). Pwnage can be attained here. [Thanks, SE!]
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Props. Thank you Dev team.
I still won't upgrade until benm solves tethering on 3.1