I've been using this exercise mat to do 30DS. I originally bought it to block my knitted shawls, but I haven't done much knitting lately. They work great as intended. They have nice support. Kinda thick and squishy. I do 30DS barefoot and I haven't had any trouble with my feet slipping. I've done yoga on them with not problem at all as well.
I can't use yoga mats their too thin and it makes my knees hurt. Luckily I found that my toddler's playmat works great! It's thick and comfortable. Too bad I can't carry it to yog class but I do use it for floor work at home!