I think Terry Pratchett is a nice and sincere man, who is doing what he thinks is the right thing in opening debate. Personally I felt that the programme was fair and balanced - although only taking up a small part of the screen time the sequence in the hospice was very powerful in showing the "other side of the argument."
But actually the whole concept of it being an argument misses the point. Many people, including Liz Carr speaking on the Newsnight discussion afterwards, seem to think that this is the tip of a "slippery slope" in which euthanasia may be undertaken against the patient's will. Interestingly, most of the religious leaders who have spoken on the subject recently seem to be avoiding the religious angle and are trying to argue on logical grounds alone, which seems a little odd to me (surely they are being interviewed because of their religious beliefs).
My FiL is progressing with Alzheimers whilst in denial and amusingly when a friend told him the other day about another friend with the illness at a similar stage he responded "If I ever get like that you must take me out and shoot me." But in fact, with someone able to humour his quirkiness and fantasies, he can and mostly does have a high quality of life. Hopefully that will always continue until he passes naturally and we will certainly do all we can to ensure that is the case.
Hopefully too, when Terry Pratchett himself reaches the point that he now feels would be intolerable, his nearest and dearest will recognise that one's concept of tolerability inevitably changes over time and with circumstances. While today's Terry may be filled with horror that the highpoint of his day may be watching some banal gameshow on TV, when the time comes he might well be perfectly content with that.
The problem is that a great many people don't have much or even any quality of life (by their own definition, which is the only one that counts) or any prospect of improvement. All of us adapt to our circumstances differently and people who remain upbeat despite adversities that would finish me off deserve admiration and support. But those who are weaker and unable to cope shouldn't (in my opinion) be made to suffer.
I have no idea which category I would fall into if the time came for me to confront these issues myself. I rather fear that I might be tempted to take "the easy option" but I guess that many people felt that way and then somehow found an inner strength they didn't know existed.
The saddest part of the programme was that it was quite clear that both men who took their own lives did so whilst admitting they felt they still had things they wanted to live for but went ahead out of fear that it was "now or never." Our laws, in both these cases, had exactly the opposite effect to the one intended.
I don't have any answers, but wish a little more genuine compassion was brought to bear on the debate.