I bought one of these back about 7 years ago and finally replaced it. Without this mat it's very hard to maneuver a desk chair (with it very smooth and easy). Always get a lot of use out of it. It pays for itself!
This is a well made quality product. Unfortunately it slides on tiled floor. I've had to anchor it down with heavy boxes under my desk to prevent it from sliding around (which was the primary reason for buying the mat in the first place).