The sound quality of the voices for the two example dubbed videos is poor, in my opinion. There's a slight echo or white noise over the voice.
This also seems like something they can grow with over time - I bought a nice USB mic because I was doing many screencasts, and the quality was much better. I'm sure over time as they grow in translators, and those translators become more skilled, the quality will go up.
Seems like a huge win-win to me - translators making higher and higher quality translations more and more quickly. I could see this driving the efficiency of the market in a great way.
I do wonder how they'll ensure quality though - are the videos vetted by anyone, both for translation accuracy and sound quality? Are there reputations for the translators? Lots of approaches, just curious which they're taking.