Courtesy of the same dudes at iPhone Dev Team, iOS 5 got jailbroken after a mere day from its announcement. The proof is the image below, showing two screens from an iPod touch 4th generation that has been jailbroken.
The info about this process came from hacker Musclenerd, who tweeted about using limera1n and tethered boot for jailbreak. Cydia and iSSH are the best indication of what’s going on with this device, that is proof of the hacking. Both these apps require a jailbreak to work and it turns out that in order to fix this iOS exploit, you need a hardware update, so you have to wait for the next-gen iPhone or iPod touch.
The version of iOS 5 used is the one for developers, in case you are wondering.