You should always check reviews online before you use an exchange. It's safer to stick with regulated exchanges like Coinbase and ecxx.
But I see many people kept talking negatively about the P2pb2b exchange which they are manipulating their IEO, from the many reviews I have observed people are not suggesting their companies for not listing their IEO in P2pb2b, so it is very good to stay away from the P2pb2b.
It is no longer news that the exchange is very shady, like you said, there are lots of negative comment about this exchange, and it is not only about their manipulative behavior on their ieo alone but also dissatisfied customers complaining about their experience in the exchange,
The other time they wanted to lunch a sig campaign here in forum without any escrow, they were ask to use one because there are scam accusations about them, but till now they never went ahead with the sig for reasons best known to them, i believe their intentions were not good.