meh, you get what you pay for on that site. I've looked at doing a couple of projects there, but the price gets cut down so much by kids who know a little bit of php and htm that it doesnt become worth while in the end. Most of the projects posted are by people who want a clone of youtube or myspace, or something so redundant you know its going to be a waste of time.
If I wanted to get some experience on learning a particular aspect of programming I would definitely go to that website to see what jobs were offered.
Thats an exaxt issue with the site. Unfortunately, the clients don't want people who wants to learn while working on the project. But thats what you get most of the time.