I just had some windows repaired by Dave and ask the question about how many have used the kit. His answer "not many". He has sold a number of kits just to have the purchaser return them and have him do the work.
I think the problem is, is that most people don't have the facilities to do the work plus it is time consuming, and takes more than one person to get the windows out. He repaired two windows of mine and and one another. Two were small and the other was a large one. I already had the valances down when he got there. He started at 10 and finished up about 4