I've been looking for something to keep my Macbook cord organized and easy to carry back and forth from home & school/work. As we all know, the little coiling mechanism on the power brick itself isn't very useful. I haven't had this product long, but I'm fairly satisfied with it. It's simple and very easy to use. I like that the rubber base has little feet, because they grip the little shelf for cables & powers strips under my desk, keeping it in place.
The downside is that it's a little bulkier than I expected. Also, from the pictures, I expected the rubber sleeve that flips down over the coil & cords to really hold the cords solidly in place. It does a decent job, but it doesn't keep the cords in the notches where they exit the coil. If the rubber were a little thicker and stiffer, I think it would really do the trick.
I'm hoping this will also prolong the life of the power supply; I'm on my third in five years, at $80 each. The power supply has a tendency to fail where the cord to the laptop meets the brick, especially if the user coils it tightly around the brick on a regular basis. If the manufacturer of this cord keeper wants to improve the next generation, I would love to have a product like this that offers some support to that part of the cord. In other words, something like a piece of plastic that abuts the brick/cord connection with a groove to guide the cord in a gentle curve when it's coiled could go a long way in preventing the cord from wearing out.