Also - although you'll never sleep on one (well, not more than once anyway) they are great on rough ground when taking a siesta - and, just found out a brilliant thing.
I bought a couple of cheap ones to cut up and glue onto boards to make display boards to fix jewellery to (no, really, works fine).
As I had quite a lot left over I couldn't bear to throw it away then decided to see what the foam is like as boot insoles. Took mine out and cut the foam to size - they are fantastic! Really comfortable, strangely non sweaty though warm. I like them so much I'm keeping them in and my anti-shock insoles can rest for a while.
I'll be hanging up the foam, marker pen, and scissors at my mobile cafe for anyone to help themselves.
Thing is - if your feet get sore there are sections of those mats you would never sleep on - so make yourself a couple of insoles!!
I know I do make a lot of jokes but this one is true!