I am building an app for the Google Marketplace and just made the switch to OAuth 2.0 from 1.0 before final deployment.
Before the switch, I was able to use the provisioning API to fetch users in a domain that has installed the app given, appropriate permissions have been granted.
My experience with the Directory API (the OAuth 2 counterpart) requires that i perform a 2-legged OAuth to get an access token which I then uses to perform the Admin action. This only works if the access token belongs to an Administrator user of the subject domain.
There's a section in the app that pulls all users from the domain and I need this to be accessible to all logged in users including non-administrative users of the domain.
Didn't have such problems when I was using the provisioning API using the Zend library