I work through Toptal. Once you get through their interview process (takes 1 month plus) I've found their team to be very helpful in connecting me to great clients. I'm in NYC and can live quite comfortably, set my own rates, and get plenty of full time work.
after wasting the time to write the sample application, my interviewer refused to even look at at it. I have seen similar stories posted here. would not recommend.
I have no idea what the interviewers motive was. I'm certain he has a different story. From my perspective he asked me to show certain functionality and then shouted over me every time I tried. After 30 minutes I hung up.
edit: obviously it wasn't personal, there is no way we had ever crossed paths before. personally I think had no idea how to conduct a technical interview and thought he was being tough on me. anyways, its just one experience. obviously people make it through the procces. I do think they could try to be a little more responsible given that they just asked for a week of your time
I can't speak for others but it's been a real pleasure to use them. The interview was a tad tedious and the project ambiguous. But after that, smooth sailing.