Bro, just to let you know , i tried to use the custom firmware 3.1 on my 3.0 jb iphone 3gs. I entered dfu mode and shift, left click restore, and got error 1600, i am just lucky that my nothing happend to my phone! and its still jailbroken with 3.0. Lots of people have already done it and are on 3.1, if you open youtube, lots of people have done it. The thing is, I would rather wait for Geohot's Jb and do it properly. Dont want to make a mistake again sigh.