I would love to see some example budgets made available for developers. Perhaps a different OAuth path that would just hand out a token instead of asking for authentication and always present the same set of budgets prefilled with sample data.
Samples could be available that use each function - the various goal types, sub transactions, scheduled transactions.
This could be used to have some easy to compare and know what you will be getting data for API developers. Documentation could also be provided detailing how each sample budget is setup.
Ideally a copy of the budgets would be created for the individual OAuth token and could be updated/modified and would be automatically destroyed once the token expires. That would allow easy testing of update code, etc and a simple enough way to get back to a known good state.
It would also make an easy way for developers to provide users with sample data to test out an application before authorizing their own data.
Just something that would probably saved me a good deal of time creating and deleting sample budgets to test out various things.