I've watched every episode from the first episode of the first series. To answer the poster who asked what the appeal is (and bear in mind I am only speaking for myself):
As a baker myself, I like to see what the bakers make of each challenge. Sometimes it is something I know I could do well and I sit in front of the TV saying 'no, not like that' 'I could do better than that'. Other times, I wouldn't have a clue and then it is interesting to learn from people more experienced than me. Though the best bit for that is always when Paul or Mary say how it should be done, either during the show or in the masterclasses they used to do at the end of the series.
I like getting to know the bakers. I feel people here can be quite harsh about people. I just like getting to know the people, in the same way that I would like getting to know any people. I can hardly think of anyone I have seen on this show whom I did not like in some way.
I like looking at the cakes. I like cakes!
I like Mary, she is a fantastic cook, a sweet woman, always ready with encouraging words. Always neatly turned out. Always smiling. Paul is a bit of a pita sometimes, but he is sometimes sexy too and he clearly knows his stuff.
I like Mel and Sue. Not the gurning nonsense, but the genuine feeling that you get that they are a good laugh and that they are kind and caring and supportive of the contestants.
There you go. All a bit schmaltzy maybe, but that is why I like GBBO. I won't watch it without Mary, Mel and Sue though.