I looked at this. In principle, every hour you have a 99% chance to win 0,00000072 BTC, which is 0,2 USD cent, so 0,002 USD.
This means that with 5 times clicking (separated by an hour) you make 1 USD cent - minus withdrawal fees AND you need to do this over 416 times to make the minimal withdrawal.
All the games they have, they claim to be honest, which means you will not win on them on average.
So although it is hard to complain on 'free money', the amount is so incredibly low that it almost costs you more in power to operate your monitor than what you make.
The choice is yours of course :)