It is an expensive detachable hard-drive but it does include Hexic HD arcade game and some videos and music. And as long as you have it connected to Xbox Live, you can download demos, game trailers, arcade game trials and some music videos for free. And later in 2007 you will have access to the Xbox Live video marketplace where you can rent and download TV shows and movies for a reasonable price!
It's also useful for storing as many game saves as you need, as well as replays, gamerpics, themes etc.
You can also store your own music on the drive for use at any time when playing games or chatting to people and it also comes in handy if you are downloading purchased or free downloadable content such as new maps, new cars and new tracks for your games.
It looks good and it's light enough to be able to bring it around with you, perhaps to a friend's home.
But, if you are connected to Xbox Live and use it quite a lot, you'll probably find that the space on the hard disk is lost quite quickly so provided you have the money, you may find a better idea would be to buy an Xbox 360 Elite console which has a 120gb detachable drive or buy the hard-drive separately.