I love my Olfa. I have the 36x24 and the two other sizes down from that. I also have the 12 inch rotary mat and the 17x17 roatary mat. My 36x24 I have had for at least 8 years with pretty regular use and I press hard with no ill effects. The mat that I had before was a Fiskars and it was terrible. I believe the Olfas are worth the money.
I will say, though, that I think the rotary mats are a little bit softer and I do see some marks in my 12x12. I use that one mostly for squaring up small blocks or things like that so I'm not too worried about that.