How are working conditions for the workers?

Working conditions at the partner factories of major brands is good.  Complicated,  high quality shoes can only be made in clean, well organized, well managed factories by skilled and happy workers.  The workers are payed an hourly wage according to China's labor regulations.  Most workers are from rural western China, and live in factory supplied dormitories.  They are provided 3 meals a day.    Workers have health care plans, receive overtime pay and have family leave .  Child labor is illegal.

That said you can find many factories with poor working conditions and less than ideal human rights.  If this issue is important to you go with a larger reputable shoe brand.  Brands like Nike, Adidas, Reebok, Etnies, New Balance etc.  have rigorous standards and only select factories that agree to follow the established policies. 

Every year over 5000 people lose their lives in Chinese coal mines.   Am I personally worried about shoe factories?   Not so much.