The Home Button had become unresponsive. I was wearing down my index finger pounding away at it.
I followed the steps in the printed guide and it went smoothly except I had to re-open the patient because I had not properly re-attached the antennae lead. With this repair and the new battery I put a few weeks ago I have anew IPhone 4!
I found having a bench mounted magnifying glass a big help and take great care when removing the many screws so that you can put them back as you found them i.e. the right size screw in the right hole.