If you noticed lately how Cydia mysteriously saves off your 4.2b3 SHSH files, well this exploit utilizes those. Patience is indeed a virtue! Check inside for full video displaying the untethered jailbreak running on an iPod Touch 4g.
Of course an untethered jailbreak is superior to a tethered jailbreak because it allows you to freely restart your iPhone with out having to repeat the jailbreak process with each reboot.
Have you held off until an untethered jailbreak was released, or have you already taken the plunge?