Since 06.15 is a higher version than 05.14 or 05.15 (where AT+XAPP is gone), anyone stuck at those versions can simply upgrade to 06.15 to unlock again! Luckily for us, Apple *still* provides the iPad FW 3.2.2 with this vulnerable baseband right from their own servers. (Grab it now, before they take it down!)
PwnageTool has been updated to version 4.1.3 to simplify the process (an updated redsn0w will be available soon as well), and you can either grab it from the official Dev-Team torrent listed on their blog, or use my personal mirror.
Great job Dev-Team!