Vantaggi
I'm an undergraduate who has some publishing experience. The work at Cactus was definitely helpful, in that the nature of it still revolves around my field. Also, some of the papers are interesting, and the pay boiled down to around 20 - 25 USD/hour, which is pretty good (I've also seen some benefits from the current exchange rate.).
Svantaggi
While this is in contrary to some of the other reviews, for me, at times, the work was excessive. I was completely exhausted for some time. Perhaps this applies to my department only, but given the number of names that appear as reviewers/crosscheckers, there is a severe lack of freelancers. Also, surprisingly, the original text to translate is often written very badly in the original language to be translated from as well.