When vetting VPN Product Vendors, what are some of the tougher questions you ask them to qualify their solutions and determine if they are appropriate for your requirements?

"When interviewing vendors to select a VPN, I try to strike a balance between making sure their products fit my needs while developing a working relationship between them and our organization. For example, many vendors claim to be IPSEC-compliant. To verify this, I ask a question like 'Can you list the other network security products with which you can communicate.' Also, as a customer, I want to know how automatic the key exchange mechanism is. In a perfect world, it would be automatic. Another question I use is that if a Virtual Network Perimeter (VNP, not VPN) is used, how easy is it to deploy the software to remote users?"