My friend recommended me to Bush at Zhang's firm. His EB1 was done by Bush and was approved within 2 weeks.
That's why I went to them for my NIW. Both Zhang and Bush were nice. Bush was really good at revising letters and writing the petition letter. And he was fast. He also replied my emails and answered my questions promptly. My 140 was approved within 20days in TSC. Of course there might be some good luck there, but I do believe that a good attorney helps a lot.
I understand that a lot of people want chinese attorney because they think it's easier to communicate. But I didn't have problem communicate with Bush. I think there are good chinese as well as american attorneys in each area, just need to ask your friends/co-workers who had good experience.