We use the big "pro" version for all our store cutting. We love it and wouldn't be without it, it allows us to make all our yardage cuts true and straight. And the Altos replacement mats are pretty reasonably priced.
One thing we did add that helped even more was putting Omni's InvisiGrip material on the undersides of the T-rulers. With long cuts on the big cutting T's it helps prevent any little side-slipping that may occur.