Most of this mining sites are a scam. Is this the exeption? I don't believe it.
It's a known ponzi scam that is no longer even paying... Well they kinda pretend to be paying by paying dust instead of expected amounts to be more exact

Total Hash Power: 2 Ths
Latest Payout: 0.0200784 BTC
Latest Payout Date: 2015-06-13 00:02:34 GMT
^^Though it does not prove the legitimacy of their mining, it proves the legitimacy of their daily payment. It is true that some old contracts from Nov/Dec did not pay well, but all new contracts are paying well for more than four months now, i.e. even after ROI.