Wow. That was indeed easy. Works fine for me on 5.1.1 on a 4S. Synced with iTunes. I spent most of my morning trying to decrypt at 5.1.1 ipsw file only to find the decrypt keys arent out yet
EDIT: As it is was extracted from the 3GS, it isnt retina-ready. Could someone please upload a retina-ready version? Preferbly in a .deb format so it gets installed to root.