Also, there's a bug currently with vCD that if you are using any IP assigning method other than "DHCP" for the NIC on the VM within the vApp it will change it to DHCP.
The hotfix for this is not out yet but you can update the DB. Here's the blog post about it -- http://veric.me/2012/12/22/vapp-template-not-capturing-nics-ip-pool-address-setting/
Eric