Can anyone tell me if the great mats are comfortable for exercising when they are placed directly over a concrete floor. We are finishing our basement and I will have an exercise room. I am contemplating whether to put thick padding and carpet or going with wall to wall great mats. I read that some people had a concern about them sliding and slipping. If I get them, I plan to get them wall to wall in my 11 x 17 room. Please let me know your opinion on the great mats. Do they make that much difference? For the last years, I have been in an area of the unfinished basement with thick padding and carpet.