They are said to be trustworthy but the contracts are not so interesting. Limited time contracts like X11 and ether are not really worth it. The lifetime bitcoin is better than the two others but with the bitcoin halving i'm not sure if it will be worth it in some time. You can improve your earnings with affiliates but then it becomes a ponzi scheme strategy (which is not nice).
My (0.21 th/s) 210GH/s of sha256 earns me 0.00012286 BTC daily (lifetime but the earning will go down as difficulty/hashrate increase)
My 1.56MH/s of X11 earns me 0.00341768 DASH per day (2 year)
My 1.12MH/s ethash earns me 0.00556791 ETH per day (1 year)
Half of what I have came from affiliates and even like that it will take some time to get my money back.
You can probably make more money from trading but it's risky if you're not sure about what you're doing.