It's a very tricky decision. When I first started freelancing, I charged a pretty low rate (~30/hr around SF), and it did get my started (getting great amounts of referrals etc). Unfortunately, I had to sacrifice my code quality b/c the amount of gigs I would work on at once in order to live here, and I noticed that the people who normally book low rate devs are the ones you REALLY don't want to deal with. So I would say never, ever ever charge a rate lower than you think you are worth. It may get you some gigs, but low rate attracts crappy projects/people. The people you generally want to work understands that high rate means better code/happier life in the long term.