I've been using two mats on top of each other for a long time..
One of gals had her revolving one at a workday and I used it and thought, humm.. nice.. later when I saw the price and went home with my money in my pocket.. I like my two mat set up even more..
Its been mentioned, but using two mats gives me much more room for cutting.. especially when I'm doing a gob of strips into squares!