Unlike the other editions, this one is untethered. Now you can reboot your device with iOS 4.2.1 without having to apply the jailbreak again. Of course, when iOS 4.3 hits, you will have to wash, rinse, repeat, but for now you are covered.
As usual, if you have unlocked your iPhone, and update to iOS 4.2.1, this ship will sail, food for thought. Follow your free spirit, and use the tool from the source link, if you are so inclined.
source: GreenPois0n via SlashGear