The metal detector has a defect - it would start humming very loudly after a few minutes of use. I've contacted the customer support and they agreed to send me a working one instead^^
My score: 11/10!
Very customer friendly, you can get a refund pretty easily here. Sometimes it's hard to log in - you have to enter the steam guard each time and the code changes every 30 seconds or so - not good for slow typers...