Pros
The contact people were very nice and were quite responsive within the constraints of the time difference with India. I loved the portal for picking up assignments and uploading finished work, filing invoices, and checking reference materials. Payment comes through in decent time. This is a good place to get schooled in medical editing and learn to work with authors who don't speak English as their first language.
Cons
For the degree of work that Cactus wants on these manuscripts, at the rate being paid, you're making far less than minimum wage by the time you finish an assignment—nowhere near industry standard, which helps bring down rates for freelance copyeditors everywhere. Cactus advertises itself as paying up to $4,000 a month, but I simply don't see how that's possible. I'm a longtime medical editor with a lot of experience in editing the work of non–native English-speakers, and I genuinely enjoyed the work, but I found the nitpicking by Cactus supervisors crazy-making. (Your pay is predicated on your quality rating, so even when you get great reviews from authors, it's in Cactus' best interest to find things wrong with your work and knock down your pay.) You will find yourself veering between having no work and having to tell Cactus to dial it back and stop inundating you with copy. The time difference with India can cause problems if you're needing help with some issue. I do not recommend working here unless you desperately need experience in medical/technical editing before moving on to a better-paying gig.