Although it has yet to be officially released by Apple via iTunes, iPhone Software 2.0 can now be downloaded through a direct link. After downloading the software image, users need to make sure the downloaded file ends in “.ipsw”, as some browsers, including Safari, will add an unnecessary “.zip” extension to the file name. You may need to look in your trash can to find the file if it is downloaded by Safari and automatically uncompressed. Once the image is ready, hold the Option key and press “Check for Update” in iTunes with the iPhone connected, browse to and select the downloaded image, and the update will commence. This image is not for use with the iPod touch, which will require a $9.99 paid update to get the 2.0 software.
Note: Apple warns in a recently posted Knowledge Base article that installation of iPhone Software 2.0 requires a complete erase of the device: “Normally if you choose to update, the iPhone or iPod touch software is updated but your settings and media are not affected. If your device currently has a software version prior to 2.0 (1.x) and you are updating to software version 2.0 or later, all data on your device will be erased in order to perform install the new software. In this case, iTunes will offer to create a one-time media backup of your device depending on what content is on your device and what content is stored in the iTunes Library you are connected to. You should ensure that you have enough free space on your Mac or PC to accommodate a backup that matches the capacity of your iPhone or iPod touch (4 GB, 8 GB, 16 GB, or 32 GB) if you proceed with the this backup.” [via Mac Rumors]