It's been quite a while since I first checked them out, and the last I knew it seemed like a bit of a race to the bottom. People competing for $2/hour made it seem like a waste of time.
Is there actually a market for highly skilled developers earning decent wages now, or is it still the same?
The main problem with these sites is not that there's developers bidding at the lowest dollar; those devs are always around, and you're competing against them even when not using the freelance sites. The problem is letting these sites own and monetize your business relationships.