thanks to great work by @comex and the rest of the iphone-dev team, we again have a userland jailbreak, and a return of jailbreakme.com. this works on all devices with most current 4.0.x iOS version. so make sure to back up your blobs if you want to keep it. (ps, yea. . . i called it. sunday is jailbreak day!)
For starters, i want to praise the hard work of everyone who made this possible. Not since iPhone OS 1.1.1 has jailbreaking been so easy it doesn’t require a restore, let alone a computer. Also, many jailbroken apps and hacks are not fully compatible with the new device/OS, be patient while developers update their apps.
UPDATE: numerous reports of FaceTime and MMS problems. I’m sure keyboards are a flurry working on the solution. if you are timid about this sort of thing, you might want to wait. UPDATE: FaceTime/MMS prob fixed to new jailbreakers. People experiencing it from earlier jailbreak, still working on a fix. Fixed.