"Cannot be combined with any offer."
I've gotten some of these types of "certificates" before from rewards sites (and I think even this exact one), and they turned out to be pretty much worthless - they won't stack with coupon codes because of the above condition. I could find coupon codes that would give me the same discount without costing me points.
So, unless I had something specific in mind to buy that costs less than about $30 or so per Shoebuys "list" price, I personally would pass.