Access USB Mode on the TouchPad
If you needed to access USB mode on a webOS phone, you could either use the on-screen option to or press the Option (orange or silver key) + Sym + U after you attach your phone the computer. This keyboard shortcut was a nice option if your touchscreen was unresponsive (or broken) since you would be unable to use the on-screen buttons. While it appeared as if that keyboard option was unavailable for the TouchPad since there was no keyboard, it turns out that there actually is a hardware option to toggle USB mode. Once you connect your TouchPad to a computer, just press the Power and Volume Down buttons at the same time and you should immediately see the USB mode icon on your TouchPad's screen.
Thanks to Rene Hennig (@renehennig on twitter) for this tip