The only one of these I have tried is coinpot. I thought it was pretty good for earning the coins and got all they offered for about 3 months last year. It was not a lot of money, but it was also not a lot of work.

But then I ended up with all kids of adware and spyware on my laptop. It started to get really slow and glitchy after this time. The guy who helped me fix it told me to stop using coinpot, so I got out of it. If you are going to do these, you should at least have some kind of cleaning and checkups for your hardware every so often :)