well if you were one of the few like me ..who has a 3.0 ECID SHSH on file with saurik ..you are able to downgrade..
you have to type a command in the terminal for itunes..so that when it goes to verify the firmware..it will think its talking to apples servers when its really talking to sauriks server and allows for the 3.1 to be downgraded for 3.0 but after it does that ..you get an error a "good" error ..and you have to use irecovery or something to get it out of the itunes logo.. but i am having trouble and am not sure what to type