[citation][nom]crom[/nom]You forgot to add: this update bricks jailbroken phones again.[/citation]
This update does NOT brick jailbroken iPhones/iPods. It will however remove any jailbreak currently on the device and if you are using an iPhone 3G with the yell0wsnow unlock, possible destroy any chances for you to re-unlock your phone.
The update does not affect the ability for the new 2G Touch to be tether-jailbroken. It also has no effect on 1G iPod's/iPhone's ability to be jailbroken, though we must wait for the iPhone-dev team to update PwnageTool/QuickPwn.