Ok, maybe we had a ton of comments about this service, here it is my experience.

I mad many investments for about BTC 1.6

1 payment out of 3 is overdue and there are  BTC 0.34 (abt 130 USD nowadays) of default payments.
 
many of the borrowers start paying and after a while, even those that seemed very solid,
pass form early payments to vanishing and never answering the payment's requests.
There is no real warranty to have back your money, the arbitration service is a pure and useless joke.
Who ever would engage in a legal action for 2 or 3 USD?
If I'll have luck and all the remaining payments will be made (and I doubt it), I will lose "only" USD 30.