I would have to say the only thing with the chair mats is unrolling them. They are so tough to unroll. Other than that they are perfect! I am so glad they have the different wood tons now.
The Staples carpet chair mat crystal clear 45x53 is the chair mat I buy for all our employees. The mat lasts a few years before it starts to chip in places from wear and tear. It's inexpensive so it isn't a big deal to replace every few years.
We got a chair mat for our computer desk over 10 years ago. It took over 8 years for it to form a spot that the wheels rolled into. The one I just got was the best one they had. It took less then 2 weeks for it to form a spot for the wheels to roll into. If I knew that I would of just used the old one.