You now have another option to jailbreak your iPhone on firmware 3.1.2. redsn0w had finally been released. It has been in beta stage but is now complete. You can download it and read more at the Dev Team’s blog at blog.iphone-dev.org. This jailbreak is like blackra1n where you don’t have to restore your iPhone in order to jailbreak. PwnageTool creates a custom firmware you restore your iPhone with. redsn0w 0.9 comes with new features like changing the boot logo! You will lose any unlocks and if you have a new iPhone 3GS or iPod touch out of the box 3.1.2, it still a tethered jailbreak:
This version of redsn0w does not provide an untethered jailbreak for those of you with brand new iPhone 3GS, iPod touch 2G, or any iPod touch 3G. redsn0w will jailbreak those but it will still be a tethered jailbreak until some new exploit is found and released.