Awesome platform!
I had submissions from about 20 designers and most designers produced more than one concept.
It seems less risky than choosing a local company and hoping they can come up with the goods.
I 'guaranteed' a winner, but it wasn't an issue because I had plenty of good designs to choose from. If you are worried you won't like any of the designs then you don't need to guarantee a winner, but you may not attract the better designers.