I have been using a K-Edge for six months, I use it every day and it hasn't done any damage to my Edge 800. Still as secure as day one. I was curious how much they are here now and found one on Amazon for $30 with free shipping. I ordered another one for my other road bike. I had read about the issues with cutting the plastic on the computer but watched it very carefully at first. I was prepared to do some light filing if necessary but I never had to do anything.
I like these DIY ones I saw on this thread.
I thought about doing one myself but I thought by the time I added up the time I personally would require to do it and the amount of blood I might lose, that I would just pay the 30 bucks.