I'm an Olfa girl myself. I have a Fiskar's mat that was given to me as a gift but have never used it. It just doesn't look like a 'self healing' mat to me. I agree w/Jan in VA that as long as you are varying where you cut and don't cut too deeply, the Olfa's 'heal' quite nicely. I've purchased mine from both JoAnn's and another LQS with equal success. I also flip mine to the plain side to extend life. I rarely use the lines on the mat for measuring/cutting except when I have to make very wide cuts for which I do not have an appropriate ruler. Then I do a 'gross' cut - over measuring by a bit and then trimming if at all possible.
I also have an Olfa rotating mat. I find that simply because of what it is and the purpose I use it, it does tend to have more repeated cut lines than my normal, larger mat. But I'm still happy that I have it and tend to be more aware of where I am cutting when using it.