I'd like to share my experience with HHS in 2012, which was an overall negative. First, the good parts. Living in Beijing was amazing - the food, the culture, everything - and I ended up staying on long after finishing with HHS. Part of my great experience was my host family, which my coordinator Maggie found for me. They were generous and welcoming hosts and made my first 3 months in China a lot easier. On the whole I had an amazing experience in China.
However, I was not impressed with HHS as a company, partly because of my own interests but mainly because of things I witnessed. In my case, I had been promised a 10-day all-expenses-paid vacation to a destination in China of my choice during my stay. However, with the end of my 3 months approaching, I was told that the company was out of money and could not afford to send me somewhere. The only option if I wanted to travel was for me to go to a lesser-known city, Lanzhou, and give a presentation to students at a college there. In return, the company extended my visa. I was disappointed, but, lacking other options, had no choice but to accept this substitute.
For others, the company's failure to uphold its agreements presented more serious problems.
To add on to my negative impressions of the company, when I posted about these experiences in a Wechat (Chinese messaging app) job group in 2015, I was amazed to receive a legal letter from HHS, essentially telling me to shut up about my experiences.
In sum, I strongly encourage anyone who is interested in China to go as an au pair - there's no better way to experience China. But when it comes to choosing an organization to go with, be sure to conduct thorough research.