The ability of virnos is that it can be deployed in any platform without much effort or expertise required from user side which makes this product very flexible as compared with other products available out there today like Cisco ASA etc., It's easy integration into existing environment also helps when you are migrating your infrastructure over different platforms/environments; I have not found anything bad about using VIRNO so far but if anyone has then please let me know because i am always open minded towards bettering my knowledge by listening others experiences too! We had some issues while integrating our vpn service provider (openvswitch) within Openstack cloud at AWS EC2 instances level where we were facing connectivity related problems between two servers running same instance type(OpenStack). With use case being VPN tunnel management across multiple environments including private networks & public clouds such us Amazon Web Services -EC 2 Instances-, Microsoft.