Apple is getting quick at closing these SHSH signing windows nowadays. 6.0.x is no longer being signed for iPhones, iPods, and iPads.
— iH8sn0w (@iH8sn0w) January 28, 2013
iOS 6.1 was released earlier this morning, and with it came the news that Apple is no longer signing iOS 6.0.1 or 6.0.2 confirmed by the developer of sn0wbreeze and f0recast, @iH8sn0w.
What this means is that just eight short hours ago you could still install said firmware on your device, but Apple quickly closed that window. As of now, if you don’t have SHSH blobs saved for your device running 6.0.X, you will not be able to downgrade.
That said, I can’t fathom a reason you would want to downgrade. iOS 6.1 was released earlier this morning, comes with a few new features, and will be the first version of iOS 6 that is jailbreakable on the latest generation of devices. If you, however, find that an app you depend on for your job is broken in iOS 6.1, you’re most likely stuck for now.