My nest boxes have those nest box mats and then aspen.
So far my eggs have been consistently clean (occasional feather or piece of aspen).
I don't wash mine, and I store them on an egg skelter on the counter.
(One egg was soiled once, so I washed it and put it in the fridge).
Of course, I don't sell mine, which makes a difference.
I've thought about getting one of those nest mats to try it out. What is yours made of? I've seen them in plastic and in more natural fibers. Right now I use dried in pellets as the bottom layer with some pine shavings on top. Haven't had any problems. But now that I have more chickens I thought I might make a change when I build the new coop. I think I'm going to make two large nest boxes rather then smaller ones, all my friends say the chickens always lay in one box anyway.