The quotes around the keys seem like visual clutter, and I wish the JSON spec didn't require them. javascript objects don't require them.
I'd like the option to not display them, and I'm guessing most people would keep it off by default.
with json-pretty-print:

With json-viewer:

What do you think about adding an option of how the key should be formatted? Or simply improving it by rendering the key in a different style and removing the double-quotes?