Overall I find the design is clean and attractive. It does a good job of focusing the user on the content, rather than distracting them with a fancy interface, and stays consistent throughout the whole site.
I do think that the home page wastes some space to the left/right of the quote. That quote probably could be positioned better to use space more efficiently, and more some more important elements up higher on the page so they are more visible.
I don’t think I like the "click to expand" links various places on the site. They aren’t immediately obvious, and I’d rather not have to search for content that should be presented to me and visible at first glance. On the home page, I would probably suggest moving the content in the "how it works if you need a design" and "how it works in 3 simple steps" into the area below the headers "Start a design contest" and "find a design contest". That information should probably be immediately visible to the user when the visit the page, so that it is obvious how simple it is to get started. I don’t think the home page explains that properly at the moment, at least, not without clicking additional links once you are on the home page.
