I was recently on a vCloud Air DR project for a customer and came across a number of gottchas that I thought would be useful to highlight.
Virtual machines need to be at least version 7 or greater in order to successfully replicate using the vSphere replication appliance to vCloud Air DR
Attached virtual devices
Virtual machines with attached devices such as serial ports need these detached before they can be replicated into vCloud Air DR
VMs with .vmdk files greater than 2TB
There is a limit on the size of disks within vCloud Air and disks that are greater than 2TB in size must be pre-created in vCloud Air DR by VMware vCloud Air Ops support in order to be supported.
None of these issues are show stoppers, however it can save you time up front if you identify any VMs that fall into this category.