Most of what I've read on the diamond rods is that they still aren't all that great for re-beveling. Even though they cut faster than the supplied grey rods, the problem is in the action (which is also what makes the sharpmaker such a precision tool for maintaining the edge).
Basically, the action of just sliding the knife one side at a time on the angled rods is pretty inefficient at grinding lots of metals. When using a benchstone or the guided rod systems, you can work at the bevel with circular motions or vertical motions and keep at it on parts of the edge and over the entire side until a burr is formed on the opposite edge and then you switch over. Even with a pretty fast cutting grit, it still takes a while to shave off enough metal for re-beveling.
I suppose you can do this by using a circular motion on the downstroke of the knife with the sharpmaker, but it feels awkward and less controlled then the standard methods above. Alternatively, you can use the diamond rods in the slots under the case and use them as a bench stone. Personally I don't find this works very well. It works in theory, but the stones shift a little bit when using the like this and the gap between the two stones bothers me. For the money, buying a good DMT course grit diamond benchstone is a far superior investment then buying the spyderco dioamond rods if the primary idea is to rebevel the knife IMO