I signed up to this last year and also barely used it. It only pays a few cents per task and although they don't take long each to do it can take a while to build up any meaningful amount of money. Useful if you're looking to outsource some of your work for other people to complete though.

It can be alright once you've been using it for a while and have a decent approval rate, then you can get some of the better paid tasks (or HITs as they call them)

It can be a good way to earn money if you're good at throwing together text quickly. There's quite a good case study on it here

Never even heard of this but I guess if it's an Amazon site it can't be all bad

I hate this site. You can search around for ages for a decent look 'HIT'. Then once you've read the instruction and click accept it's already been taken by someone else. Not worth the time and effort.

Crappy work for crappy money

Probably about the worst thing Amazon have to offer

You spend more time searching for tasks to undertake than you actually spend doing them. Well frustrating and not worth the effort.