According to MuscleNerd the Gull1hack utility is fake

Gull1hack, the tool that promises to jailbreak all iPhones and iPod Touches with the latest iBoot, is a fake. Here is a twitter comment from MuscleNerd, hacker from DevTeam:

It looks like the guys who created Gull1hack used two different iPhone 3GS's (or perhaps 3GS and 3G) - one with the old iBoot and one with the new one. Here is a quick conversation between MuscleNerd and Gull1hack: