The iPhone Dev-Team has released redsn0w 0.9.6b6 for Windows and Mac with a new tweak that avoids the issues like battery-drain and overheating that plague unlocks. Rather than using redsn0w to hacktivate, this version lets users click a "Deactivate" button to remove the patches that affected battery life and push notifications, allowing @sbinger's SAM tool to do the hacktivation.
Sam (@sbinger) Binger, the developer of TetherMe, came up with what he calls Subscriber Artificial Module (SAM), which tricks iTunes and your iPhone into generating official activation tickets even though the unlocked device carries an unofficial SIM. As a result, the lockdownd patches that were required to make hacktivation work with redsn0w are no longer needed, and unlockers can use SAM to hacktivate without taking the battery life hit.