Well, I have seen quite lot of these "concerns", and the short answer is "Yes".
There are labor workers working like slaves in China, as described in the article. And the number of these workers and companies are huge. It is bad. I agree on that.
Don't look at China using the US eye please:
From our (Chinese's) perspective to see it, the positive side is not only "they are hiring", it means more for China. Those labor workers are mainly from the very poor village (farms), very few of them are from the cities. In China, the population from the poor village is still high, much higher than you can imagine (maybe 30% of all 1.4B). They can't earn a living if just working in the farm, they can't raise their kids or support their parents if just working in the farm. Those companies provide them the job, though with very touch condition.
Let me do the math for you:
41 cents per hour means 0.41x12x6x4 = 118 $ = 826 RMB / month. this is the net pay (take-home pay after tax, insurance,..). (this example is a bit low. More often I heard is about over 1000RMB / month.) anyway, you know the value of that in China? It means 800 $ in the US. With that, you can not have a perfect life, you can not afford a car, but you definitely can live (even in big city like Beijing). Furthermore, if they bring the money back to their village, the value is much much more (in some village, 10 US cents is good for a one day expense. i am serious. It is China, don't look at China using the US eye please.) . So this is related to the currency value. 41 cents/hour looks very very low in US. but remember, it's different in China, Its value is more in China, and much much more in the poor village.
I really don't like that some western "journlist" ignores the big currency conversion (1$=7RMB) when they are talking about this bad companies and 41 cnets/hour. While, on the other hand, they look so closely on the conversion rate, complain the conversion rate is too high and should be 1$=2RMB. This is idiot to me. they don't really know about China, they just want to make anything in China negative.
From my once a year trip back to China, I can see clearly the life of the peasants from those villages is improving a lot year by year. The main main reason is not China cuting tax for them, is not China running a stimulas package for them. The reason is they, by themsleves, go the city to work in those "IT" compaines. They should (i agree) earn more and the pay that they deserve is much less. But this is the start, they have started to earn much more money. They have started imporving their life a lot. Those companies are bad, but they are providing oppoturnities.
Talking about China development:
I am not saying those companies are doing the good thing. They are in guilty. China is still in the middle of development, not everything is perfect, especially we are lacking a lot of rules and laws. There are bad companies taking this as an advantage and making huge dirty profit from the poor labor worker. but from my perspective, it is a step of the development. We can not make all the companies to be good ones. There are bad ones existing. But those bad companies are also helping China and helping those poor people to improve their lives, although the companies should improve their lives much better (by providing better pay to them). I believe China is working very hard on making the regulation better to make the poor labor workers earn more and more, and make the whole system more healthy.
Anyway, this is just from my (a native Chinese's) perspective. You (western people) may not understand it, but i want you know what I think.