Just letting you know that the reason you are probably not receiving any responses is because nearly every question you ask is either easily Google-able, or you are asking for opinions versus facts.
Want to know if IPv6 is secure? Do research to find out. Then you will know for sure.
This comment gives very little to the discussion. The original poster had plenty of valid questions that are very hard to find the answers to as its mainly enterprise/business systems.
I would say you will have a hard time figuring anything out for yourself when your infrastructure uses business-class solutions and is cross vendor.
Want to know if IPv6 is secure? Do research to find out. Then you will know for sure.