When shopping for an e-discovery vendor, always ask to interview their experts, the ones who will actually be assigned to your case. You should do so for any significant purchase, but especially for review software or a large search and review project. That should be part of your standard due diligence.
Ask the vendor questions now, while their meter isn't running, and while there is still a chance to select another vendor. The same can, of course, be said of a client selecting a law firm. Can you understand what the alleged expert is saying? Does what he or she says make sense? If not, it might not be your fault. You might not be not talking to a real person at all. You might talking to a parrot. They might look good, and sound good, but all they can do is memorize and mouth the words of others. They do not have any real understanding of their own. That is just the way parrots are. When push comes to shove, they will not be of much help.