Hey Poppy Fields,
I haven't had cancer, so I can't say how I would react to the show if I had. I do think the show is definitely not for everyone. Showtime has a certain style to their series shows. You can see it with Californication, Weeds, Nurse Jackie, etc.
Showtime pushes the envelope very far, perhaps too far with their programing. They tackle issues like professional women having affairs, stealing, and being a drug addict. They have a show about a serial killer you are supposed to like. They have a show about a drug dealing, pot smoking mother of three. Most of the shows are quite daring and insulting to some people. I don't think the Big C is any different in that respect. I can see why some viewers might not like it. I will say that I think Laura Linny is just great in this role.