Avantages
Upwork is the biggest player in the space. They provide free food. No accountability. Many folks just "work from home" many days a week, or come for a couple hours. Good place to retire if you do not mind drinking a ton of kool-aid and obeying questionable orders.
Inconvénients
The new CEO is not very good. He rewards mediocrity and punishes competence. He hired an army of very cheap, but mostly demotivated (and in some cases incompetent) freelancers from the most disadvantaged countries he could find, and tries to run engineering with them. The reality is that most freelancers care about their hourly wages, but not about quality, good engineering practices, or timely delivery. Engineering teams pretty much never deliver on their goals, have terrible engineering practices, and can't even keep the site up for a full week without major (multi-hour) outages. Half the projects that are started are failures, the other half are late by months and delivered with tons of bugs and poor non-scalable design. Most of the code is written in Perl using ancient and arcane practices, and poor documentation. This plus the high rotation of the freelancers makes it so that in many cases nobody knows who wrote the code or what it is supposed to do. A lot of effort is put into chasing down major bugs written by people long gone, and an owner who is asleep and non-responsive somewhere on the other side of the world. They had a few competent people that came with the Elance acquisition, but the CEO made sure they left in a hurry.