All the times I have been offered an extend warranty plan I turned it down except once when I bought a digital camera and then I never used it.
I don’t think I would ever get another plan, so I would say no but I do not have experience with HD warranty and with your recent needs of repairs it does sound like a good idea.
How has your experience been with the regular warranty and do you think you will receive the same satisfaction for any future repairs over the next three years?