We also used it for one of our upcoming sites and were quite pleased. I spent an incredible amount of time providing feedback to the nearly 40 designers who too

We also used it for one of our upcoming sites and were quite pleased. I spent an incredible amount of time providing feedback to the nearly 40 designers who took a shot (over 136 revisions). Still, it totally paid off and we came away with 4-5 we would have been happy to use. Just keep in mind that you get even better results if you work with your designers to nudge them in different directions of your preference. We also did a trick of offering to pay for two logos. This made the grand prize lower (because of our budget), but it created some great competition.