Rated 3 out of 5 stars
Splitting the screen is the way to go with a widescreen monitor. It's nice to have a chat or video rolling on one side of the screen while I continue my internet toiling on the other. Very useful add-on.
However, because of a glitch or design flaw, I cannot unsplit the screen when I want to go back to a full-screen view. There is a close button, which presumably is there to close the split window, but clicking it does nothing. The only way to get rid of the split is to close or restart Firefox. Very frustrating.