This wonderful discovery was publicize via Twitter today. Surely very helpful for iPhone 4s and iPad 2 that using iOS 5.1 and now are unable to jailbreak their device using Absinthe (for Windows and Mac) tool to install Cydia and have an access to that app's store, of course after they managed to downgrade their existing iOS 5.1 to iOS 5.0.1 using the exploit that iH8Sn0w has found.
However there is no further details what the iH8sn0w's downgrading tool might be and when it will be made to public. But once it's released, you can downgrade to the iOS 5.0.1 and then untethered jailbreak your A5 devices. Because the iOS firmware version is jailbreakable iPhone 4s and iPad 2.
And be sure you've already saved the iOS 5.0.1 SHSH blobs as it's likely the must have requirement for downgrading from iOS 5.1 to iOS 5.0.1. So if you have it, then you are ready to go when iH8Sn0w release it for public usage.