The OcUK Mega Mats are really very good. I had the much older previous model without the stitched edge and it did eventually start looking tatty as the top layer began lifting at the corners. That was after years of abuse and washing machine treatments mind! I have yet to put my new(er) stitched one in the machine yet, as I've looked after it much better, but from everything I hear they are far more robust.
If you're in the market for one, and find yourself uhhming and ahhhing about which to get, just get the OcUK one. It really is tried and tested and is great value too.
I really notice the difference when working at a desk that isn't mine. You'll never want an unpadded desk again!