Here's the latest from the jailbreak source (via the Wired article, below):
[iPhone Dev-Team member Eric] McDonald explained that current tools will still work with the latest batch of iPhone 3GS units. The “24kpwn” exploit used to help jailbreak previous iPhones and iPod Touch devices only made it easier to boot up the hacked devices.
The newly shipping iPhone 3GS’s bootrom interferes with 24kpwn, but that will only make the handset difficult to start up after it shuts down. Booting up will require being “tethered” to a computer. That means if you shut down a jailbroken iPhone 3GS, or if it runs out of power, you can only turn it back on by plugging it into a computer.
Is this latest 'tethering' hurdle something linux can handle?
By which I mean, if an iPhone owner that only runs linux needs to reboot his device, can he perform the legitimate 'tethering' routine on his linux box?