IPhone :: Method To Downgrade For MAC

Eager to try the next iPhone/iPod update? If you upgraded, but can't activate the phone, you are stuck, so the logical thing to do is go back to the old firmware and wait until it's officially released, but going back is downgrading. That's where you get stuck. So here is an easy and working method to downgrade. If something doesn't work, or I'm wrong about something, please let me know. This guide is for Mac only.

Step 1) While the Phone is plugged to the computer, hold the home and power button until the phone goes off and comes back on. When it does come back on and the apple logo shows, release just the power button. The iTunes logo should soon show up. (This puts the phone into device firmware upgrade mode which allows us to communicate with it)
Step 2) Download Tools.zip attached and make sure it's in your Downloads folder. (This makes sure we know where they are so we can direct services to it)
Step 3) If it's not already unzipped, unzip it (To access the contents)
Step 4) Launch Terminal and type/paste: sudo cp ~/Downloads/Tools/libusb-0.1.4.dylib /usr/lib (This command moves a file which allows us to talk to the phone through the USB port to the appropriate location)
Step 5) Enter Your password as prompted then hit enter (This gives you permission to move the file)
Step 6) Make sure you have hit enter and gone to the next line then type/paste: ~/Downloads/Tools/./iRecovery -s (This is the tool engineered by wEsTbAeR-- and Tom3q that allows us to talk to the phone)
Step 7) Terminal should now display information about the phone and the last line should say "(Recovery) iPhone$" if it does, type/paste: setenv auto-boot true (This tells the phone to stop going into recovery mode)
Step 8) Make sure you are on the next line and type/paste: saveenv
Step 9) If all went well you should be able to boot your phone by holding the power and home button until you see the apple logo. From there on you can activate and sync.

I just came across a script AppleHack23 is distributing (Probably created). I haven't tested it, but it looks like it only sends the commands to the phone, so you can use it after Step 5. (Direct download for the script)