In the late 80's/early 90's I was working for a little electronics manufacturer that also sold Color Computer software. I remember all the phone calls and letters asking for support and there was one lady in particular whose complete address I remembered because she wrote us so often, trying to get her Digitizer working. She was finally successful and pasted a scanned photo of her daughter in a cowboy hat into her final thank-you letter :-)

One of the lessons that stuck with me all these years is that quality of product documentation/ease of use is inversely proportional to the number of support calls I had to take.