Yesterday, we told you that Apple dropped iTunes 9.2.1 and it should cause no problems for jailbreaks, but you should wait for the community to fully test it before updating. Today, MuscleNerd announced that iTunes 9.2.1 is fine for already-jailbroken devices and also new jailbreaks via redsn0w/PwnageTool.
You should avoid this update for now for fresh Spirit jailbreaks. That means that if you own an iOS devices which cannot be jailbroken right now, and you are waiting for the new version of Spirit, you should NOT update.