I disagree with the "shave it all" crowd.
As a professional groomer, I hate shaving cats. If I can remove the matting without stripping the whole cat, I'd definitely do it.
Don't worry, shaving was definately the last resort. I even tried my hair detangler which worked on some of the matting but unfortunately not the worst areas. I am pleased to say that even after shaving her, as soon as I say hairbrush, she jumps on the table ready to be groomed. She really is a sweetie and has the nicest temperment in a cat that I have ever seen.