Pros
There is generally a good supply of work. The interface works reasonably well. The pay is acceptable and one can make decent money if you're good. You can set your own hours. Since a lot of the content to be transcribed is from universities, if you happen to have some technical or scientific knowledge you can make a very tidy amount of money. Business appears to be stable, I have made good money from them over the last four years.
Cons
The company is sketchy. There is no contact information for anyone on their website. For all I know it's just an automated program running on someone's computer somewhere. Their bonus system is designed to make it as difficult as possible to claim bonuses, which make up a solid portion of your pay. The quality control system is a catastrophe. There is no oversight. You submit a task, someone else scores it. If the score is too low it may bring your average down to the point where you lose your bonus. You have a limited number of scored tasks that you're allowed to dispute even if the reviewer was blatantly in the wrong. You need very good headphones and a very good keyboard to be efficient at this. I have a Cherry MX Blue keyboard ($160) and a pair of OPPO PM3 headphones ($400). You will not be able to do this with your laptop and a pair of earbuds from Wal-Mart, and if you do not already own such hardware it's probably not worth the investment. There is opportunity for advancement but it is completely unclear how one is supposed to ask for a promotion given that there is no apparent way to contact management.