Yes, I strongly concerned about the private key supported wallet.
BTW, I'm happy to see and introduce such of wallet information. I just ask http://coinpayments.com/ have any bad reputation. I also introduce this wallet service which also supports many coins. Has anyone used this service?
Here are some of the coinpayment's concern thread here and you might want to take a look.
https://bitcointalksearch.org/topic/coinpaymentsnet-scam-stole-650-btc-1694776
https://bitcointalksearch.org/topic/coinpaymentsnet-scam-1633974
https://bitcointalksearch.org/topic/coinpaymentsnet-complete-scam-artists-complaint-withdrawn-1546008
https://bitcointalksearch.org/topic/coinpaymentsnet-unbiased-unified-money-solution-multi-payment-procesing-276455
Coinpayment Support: https://bitcointalksearch.org/user/mrdata-193932 - MrData