Let me begin this review by saying this is a great product and very useful, a must for anyone who regularly uses their Wacom tablet. Now that that's out of the way, on to the review !
Nibs: Always good to have more!
Rubber Sleeve: I have never had a problem with the side switch, but I know of people who kept accidentally clicking the switch while they were drawing and found this made their tablet more enjoyable to use.
Side Switch: Although I haven't had to replace my side switch, it's nice to have, just in case.
Nib Remover Tool: By far the best part of this kit is the nib remover tool. It's simple design allows easy removal of all nib types (at least compared to the pair of tweezers which gouged one of my nibs).