I have tried it for a couple of clients just to see if it’s worth my time and $, but my personal opinion is no. Unless you are willing to negotiate your rates and then drop them enough so you can win the bid, it’s not worth the time (and I wasn’t going to do that). But this is just my opinion.
I’ve been using it for a few months now. While it can seem to be a bidding game to some, I use set rates and don’t really negotiate. If a client wants my services they will contact me, if they want someone cheaper, they will contact them. If you, as I, feel as though you are charging the appropriate price for your services, there is no need to bargain price yourself. I have gained a few clients from the service, but I have been a little more selective to the requests that I respond to now also. Give it a shot, you really have nothing to lose but a few dollars and some time checking the leads. If nothing else, it’s getting your name out there to more people too.