I put Pergo on the floor of my 13' Scamp. Came out fantastic. Did the entire floor. Easy to do and looks great. The original carpet was still in the trailer and it just dated it. I don't remember what the cost was, but it is cheap. Just take your time and refuse to be in a hurry. Nice part about it is that if you mess up somewhere, just chuck the piece out and cut a new one.
I like the idea of Pergo floors in our 5er. Lynne's not so sure, but since (at the rate I'm going now I have the loft done) I have something like five years of project ideas in queue for the trailer, I can wait on Pergo floors.