not worth it unless you live in a developing country. i did a few projects on there back when I was in school. what a rip off (don't ask). that was like 6 years ago. I imagine it's even worse now.
if you want experience, frankly I think it would be better to work on open source projects for free. that way you at least aren't subject to menial work and ridiculous demands for a few measly dollars. if you wanted to support yourself, a minimum wage job would pay more.
I'm not saying it's impossible to make decent $$$ on there, at least the last time I saw it. if you have a lot of experience and/or a good portfolio, and know how to market yourself, and spend the time building up your reputation you could possibly make some $. but it'd probably be more satisfying and profitable to direct that effort elsewhere.