I bought a martelli mat and it was so much nicer than the fiskars/olfa I had used in the past. Not even a close comparison. That said, I wanted a mat to cover my entire cutting table so I got a custom cut Magic Mat and I really like it so far.
eta: I also have the martelli rotating mat mentioned above. I bought it from martelli during a 50% off sale. I like it so much I bought one for my sister during the next sale.