I wonder how often it'd actually come up that you could get stuff through your application layer into the database and/or back out without wanting to tweak it first. Where i have Rails JSON api's, I usually do some tweaking/modification of the JSON that comes out, for instance.

I don't think I'd ever want to _serve_ json from the db, and as you say, I'd tweak the data for common usage anyway.

But my use case is the opposite: I am storing exactly the data coming from external APIs.

My table has some fields I already extracted from the JSON data, cause I need them now, yet I don't want to throw away the full data, as I may need it in the future.

So, I was storing the original JSON as text.

But, having support for the API format in the db itself is much better, as I can also actually query and manipulate this data without pulling all the text fields in my client code.

You may want to look into using postgresql functions to modify the json that comes out. Probably much faster, especially if you have lots of nested stuff coming from different tables.

heroku has unofficially supported 9.2/json for a couple months.