I have been playing around with this lately and have had it for a couple years. Its a $30 set of plastic clamps that allow you to do things with CDC that is amazing and allows you to maximize the use of CDC feathers. Its a rather simple set of devices and I wholeheartedly recommend it if you like to use CDC flys. Personally I have been using an all CDC caddis dry fly out here for the past couple seasons...nothing floats like this fly..you cant sink it until a fish slimes it. The magic tool allows me to use CDC as a hackle, body or wing...the flies look super buggy and work really well. You can see an example of the use of the tool on this video
Tie your flies with the magic tool
One of the real keys to tying with CDC is to use good feather...Trouthunt.com is Rene Harrops shop in ID and has the best domestically available CDC. Petitjean sellls his through hareline dubbin...as MP Select CDC...both of the above are far better than the run of the mill stuff most shops stock.
I also think Petitjean has the sickest vise available...(not the one in the video) but this one..
http://www.petitjean.ch/eng/MPVise/masterVise.asp
anyways...if you like using CDC you will really like using the MagicTool..