When I first heard about this I doubted the need for one.
But then I gave it some thought and came to the conclusion that it's a very
worthwhile accessory for 360 owners.
One of the annoying things about charging the wireless controller is having
to have it plugged in via a cord which goes to a USB socket on your 360 (even a
PC is possible). So in effect your wireless controller becomes wired whenever it
needs charging at the same time you wanna play.
But with this charger which comes with a second battery you can charge two
batteries at once, then place one of them into your wireless controller. Once
the battery get's low you can hotswap it for the other charged battery which
means your controller stays wireless 100 percent of the time.