I was given one for DD, I loved it. Gave her a bit of padding, stopped the seat being hot/cold, stopped her sucking on the sides/handle (she did that a lot!), and caught anything she had between the seat and the handle.

When DS was in the lay back seat thing I just put a blanket in there, but now he's in the seat next to DD I can't use it. I had no idea you could get double ones, I'd love one!