My favorite is a Martelli cutting mat. I don't think it will ever warp. When I bought it at the Dallas Quilt show years ago (probably about 7 years ago - at least) the salesman literally rolled it up and jumped up and down on it and it just unrolled flat as could be. It is self healing and I do a lot of cutting on it. I've never had any problems with it at all. Of course it is always on top of my cutting table and not one of my traveling cutting boards, but for those I like the Fiskars.