Pros
Flexible schedule. It helps if you really need the money and you have all the time in the world, or if you are working remotely and in front of your computer all day anyway, and if you live in a low-COL country, relative to the USD. Learning about interesting industries. They pay weekly (on Thursdays) at your request, min 10 USD. And they do pay the full amount, but they round down the decimals which could easily just be left in the account.
Cons
Very little work, very low pay. You'll be working for - best case scenario - 2 dollars an hour. Entry exams are quite hard, no feedback, no training. Advancement exams are even harder, no feedback, some information is unclear, and most are usually unavailable. You'll spend a *lot* of time studying for those, and you get nothing in return, even if you only failed one question (even when the names on the exam and the Guide don't match, so you have to take a guess). They don't pay extra for the bad - sometimes horrible - quality audio or thick non-English accents (even thou you should take exams and charge more to get those, according to their website). No extra pay for rush jobs either, which will be the only ones you'll get 99% of the time, and you can't stop until completion. If you take a few minutes they reassign them. That means you have to be constantly sitting on your computer. I've spent more than 16 hours connected without getting a single job. Some QAs (responsible for approving your work) don't keep up with the changes in the Style Guide, so you might end up with a worse rating than you should, and sometimes they'll deny you pay (you can appeal, and some support people are great, others are not). So you might get denied a payment of 50 cents for a job that took you an hour due to the audio quality. If it's too bad you're better off declining the job, at least that's what I do.