Why pay more than you have to for a chairmat of all things?!? Everyone in our office is average size (150 - 250 lbs) & we haven't had any problems with these chairmats cracking or showing stress marks. As our office grows we will purchase more of these.
So far this has been a great product. I purchased it to protect the new carpet in my home office and to allow my chair to move easily. I will have to wait to see how it wears over time. The only drawback is that the back edge is not straight - it was made with two small circles (possibly for hanging mats in a store display?) that jut out preventing a smooth line on the back edge - which is the edge that is out in the room and therefore more noticeable.