Sure, this has been posted already, but I’m hoping to simplify things for you with the full instructions on my site. I definitely don’t want you wasting your valuable time like I did. (Note: I successfully upgraded to iOS 5 on my iPhone 4 and my iPad 2, but so far I’m 0-2 on the 3GS upgrade.)
Now I know what you’re thinking–and yes–you could just wait a week to upgrade the easy way in iTunes, but if you did that, would you be way cooler than all your friends? Of course not. Now, let’s continue.
Step 1 -Download the firmware for your device below:
iOS 5 GM for iPhone 4 (GSM) – AT&T
iOS 5 GM for iPhone 4 (CDMA) Verizon
iOS 5 GM for iPhone 3GS
iOS 5 GM for iPad 2 (Wi-Fi)
iOS 5 GM for iPad Wi-Fi + 3G (GSM) – AT&T
iOS 5 GM for iPad Wi-Fi + 3G (CDMA) – Verizon
iOS 5 GM for iPad 1
iOS 5 GM for iPod touch 4G
iOS 5 GM for iPod touch 3G
Step 2 – Download and install iTunes 10.5 beta 7:
Step 3 - Load iTunes with your device connected.
This is where there magic happens. Once you’re up and running, click on your device name in the left sidebar. On the device summary page you will see the Restore button. Hold Option (Mac) or Shift (PC) then click the restore button; the click will pop up a window where you can select the firmware to restore. Navigate to and select the firmware you downloaded; click Ok.
The installation process has now begun; there’s no turning back now. The progress bar on your device means that you’re well on your way to the iOS 5 promised land; no progress bar means FAIL.
The device will then restart a few hundred times (actually, only 2 times), and then can choose to restore your data; select your previous device name and click Ok.
Once your data is restored (and restarted again) iOS 5 loads up with a few welcome and setup screens. Complete those and then you’re ready to rock!