I use this all the time! This little widget installs and works instantly, turning the developer's mode off and on so you can drag widgets out of the Dashboard and onto your desktop.
I frequently want a widget on my desktop instead of having to go back and forth to the Dashboard. For example, Sing That iTunes. I want to play my iTunes and have Sing That iTunes add lyrics to my database in the background, but it can't do that if I'm working on the computer and the Dashboard is not active. I use DevMode to drag Sing That iTunes to my desktop and I'm getting lyrics all afternoon! when I'm done playing music, I just drag the Sing That iTunes widget back to the Dashboard.