iH8sn0w has posted a tutorial on pwning an iPhone 3GS with the new bootrom, something PwnageTool can’t do at the moment. The phone must be downgraded to 3.1.2 first, and there is no tool available, so it will all have to be done by hand in a little over 20 steps. It involves using SHSH blobs, running a few different applications, and rolling a custom ISPW. If you’re up to the challenge, follow the link and good luck! Some of the apps required are Windows only, but a tutorial for the Mac is on its way.