In many ways this is one of the best services of this kind around (at least for the sellers), but be wary: they are very clingy, and it's reflected in their rules, so read them carefully.

It is mentioned that if you use another trading platform of this kind other than theirs - they will block your account and refuse to allow you to withdraw funds from it, and there is really nothing protecting you from such behavior on their part (it's in the rules after all), so if it happens to you - you're losing the money for the service/goods that you've already provided.

While it is in the rules, it is also akin to your girlfriend threatening to burn your house if you start dating someone else, which is really weird and creepy.

If that still doesn't stop you from using this service at least be cautious, withdraw money as often as possible, so as not to allow them to steal from you.