I wrote them late last week to ask if I could provide a part-public key to have them generate an address with and they have not replied.
If they wont do this, then any address they generate is only as secure as their software, your e-mail and the internet.  That being said, they do use a secure server and if the software is fully automated, human eyes might never see the private key.  If it comes down to guess work though, you can never be sure your coins are safe.