The diamond rods are very, very coarse rods that are meant to help you reprofile your blade. They are not meant to get a blade sharp - that is what the medium and fine stones are for. All they will help you do is change the angle of your edge much faster than if you use just the medium stones. They are worth it if you have some very, very dull knives you want to resharpen, but otherwise, I have found the medium and fine stones to be plenty for sharpening and maintaining an edge on all of my knives.

One thing you may want to consider is the very fine rods instead of the diamond rods. I have not used them yet, but I hear they somehow manage to make your already razor-sharp edge EVEN SHARPER <img src="/images/graemlins/shocked.gif" alt="" /> <img src="/images/graemlins/wink.gif" alt="" />