If you want to jailbreak your iPad or iPhone to use some of those cool jailbreak hacks we showcased last year, but you already upgraded to the latest v 4.x firmware, you are in luck. An (untethered) iOS jailbreak is now out for v4.3.1.
It still doesn’t work on the iPad 2 (fix is forthcoming) or the Verizon iPhone, but covers everything else.
Dev-Team recommends you use PwnageTool or redsn0w to jailbreak and hold off on using ultrasn0w.