99designs has a couple very helpful functions: 1) Ability to create a poll - this was incredibly useful for obtaining feedback from outside sources. 2) Customer service chat function - my questions were usually short and simple, so the chat function provided a quick and easy way to get those questions resolved.
Product : Got tons of design proposals on the contest. For the first day or 2, designs would trickle in and I'd provide feedback. The last couple days is when multiple designs start coming in all at once, so I had lots to choose from. It helped to get frequent email updates from 99designs keeping me up to date on the contest and letting me know if I had new messages from designers.