I don't do a ton of doors so I have been getting by with hole saws and such.  Hole saws take a lot of time and they can be difficult to perfectly line up from one side of the door to the other.  I finally bought this kit and man what a difference!  I have used it for about 16 doors so far and it is one sweet tool. Each door has come out perfect. I used to fear doors, now I actually look forward to doing them with this tool and my Porter Cable plane.  I will buy the carbide bits when the steel bits start getting dull.