Up until now, only older iDevices have had the ability to downgrade to previous firmware versions using the Limera1n exploit and SHSH blobs, but that ability has now been ported to newer A5-powered iDevices like the third-gen iPad and the iPhone 4S.
Did you upgrade to iOS 4.1 only to realize that there was no jailbreak available for it? Do you miss all of those unauthorized apps that you had previously? Fret not, my iPhone-touting friends, because now you have at least two options for breaking free of those shackles. It was only yesterday that we caught wind of the Limera1n jailbreak solution, and now today, you get another shot at the steel bars with the GreenPois0n tool.