The Dev Team just released the Pwnage app, which jailbreaks 2.2.1 iPhones on Macs. If you're ever going to SIM unlock your phone in the future (use it on another network), use this, not QuickPwn.
For people with 10.5.6, you're going to have to re-enable DFU mode in order to run Jailbreak. The Dev Team blog has instructions on how to do that, but after you're done, you should disable DFU mode by running the steps backwards, as we documented here. It may screw up your machine if you don't. [iPhone Dev]