I've been having good luck with the API so far but ran into an issue trying to instantiate a vApp from a template, using version 1.5.1. InstantiatevAppTemplate() throws a VCloudException with the message - No access to entity \"com.vmware.vcloud.entity.vapptemplate:blahblahblah" I'm logged in as an OrganizationAdmin. So I don't believe permissions is an issue. The same user can create vApps through the Web interface with no issues.
I'm using NewvAppFromTemplate() method from teh HellovCloud example. Any help is greatly appreciated.