I have the one from Joann's but I don't have enough experience with any other to know if it is dulling my blades. http://www.joann.com/36x59-cutting-mat/xprd74039/

The description says "great for rotary cutters & blades"

I have noticed my blades get dull fast, and thought maybe the 60 mm blades get dull faster than the 45 mm blades I used to use. Now I'm thinking it is the mat. It definitely is not self healing!