I can not answer the question of factory slaves, but I did a research paper while in college on the subject of slave life in the south (field slave). I was surprised to learn that it wasn't as bad as I had thought. (NOTE: I am NOT saying that it wasn't bad, just not as bad as I thought.)
I would recommend a book called "Twelve Years a Slave" by Solomon Northup (Available from Amazon.com for less than $10.00). This was, for me, a very easy read on the subject and I believe it to be a true account of his 12 years in slavery.
While most people tend to think of the huge cotton plantations with the evil slave owner with hundreds of slaves, many of the slave owners owned less than 10 and worked in the fields along with them.
The rampant beatings (that go along with the huge plantation version) probably weren't as common as I thought. You depended on this person for your livelihood - why would you beat them to death? I am sure that there were some beatings for escape attempts, disrespect and the like.
I was also surprised to learn that there were instances (by some slave owners) to allow their slaves to make furniture, quilts and other things for other people. Any money earned could be kept by the slave in order to buy their freedom. (I am not sure how wide spread this practice was, but it is mentioned in the book I referenced and was also mentioned at a museum gallery I attended a couple of years ago). Some were even allowed to go to "parties" to work - also getting paid for this.
I am sure I will catch some flack from some people, so let me clarify: I DO NOT condone slavery, I do not support slavery (and lets face it, it is still around in the world today), and I think that it was one of the darkest periods in our countries history. I think it was a product of its time in the US and for those who want to condemn the US for participating think of this: The US couldn't have had slavery of the African people, if it weren't for the people of Africa selling their own people into bondage.