I have. It was a long process, and since you have no access to the candidates past jobs, b/c freelancer.com wants to avoid providing you with a way to contact them directly, you have do good questions in your posting. I suggest this because their responses, way of writing and such, will let you see some of their qualifications and begin the selection process.
Of two posts, I only hire on one post. In the other post, I did not find a suitable candidate, but still had to pay the fee.
It was a good experience.