Hi. I realize your post is a bit old, but I thought I'd respond anyway.
We had a Casper mattress, but just returned it. It was much too soft for us. We were referring to it as the Marshmallow. If you like a softer mattress, this might be something you'd like. Also, the top layer is made of synthetic latex, and I apparently don't like that kinda bouncy feel. So it didn't work out for us.
I read a lot of reviews on their website and some people felt the mattress was too firm. So I guess it depends on one's perspective.
The people at Casper are very pleasant and accommodating. We were able to return the mattress without a hassle. Someone came to pick it up and we're getting a full refund. Also, since we're in NYC, there was no charge for either the delivery or the return. I'm not sure what their policies are for shipping outside the 5 boroughs. You'd have to check.