I only use Alvin mats! They are double sided, professional grade and every bit worth every penny. Course, I don't pay full price for them~I buy them from the college bookstore! The price is $22.30 for the 24 X 36!!! I live in MT, so not even any sales tax!!!
I have been using them for years and swear by them! The only problem I have is that the last time my Step-daughter brought me some home, they managed to get a little warped, I cannot unwarp them! I buy several throughout the year and sell them (at the same price I pay) to the gals in my quilting group. There is some great info on them in this link.
http://www.quiltingboard.com/t-59896-1.htm