I didn't get mine yet. They are supposed to be 99% cotton, 1% spandex. Guess we will see. I would have thought they would have arrived by now, as I got a shipping notice the same day I ordered, I think.
I would say to keep you jeans if they look good. They were a great deal. You could always wear them around the house for a few hours and see if they stretch out too badly.
I bought my current pair of Sweet n Low's on eBay, and they definitely felt different from the jeans I had tried on in the store. I wondered whether they might have been the cheaper versions that are sold at Costco, etc. But in the end, they looked nice on and I had gotten a great price, so what the heck. They do stretch out a bit by the end of the day, but it doesn't bother me that much.
Mom to DS1 (3/06) and DS2 (9/08)