I recently started using the "New Google Sheets" (spreadsheets) and they changed the URL to a shared public spreadsheet and I am unsure how to obtain a JSON feed of the spreadsheet data.

Based on data from this URL: <https://developers.google.com/gdata/samples/spreadsheet_sample>

I can obtain the JSON data from an older version spreadsheet using the key parameter found in a URL of this format: <http://spreadsheets.google.com/feeds/feed/key/worksheet/public/basic?alt=json-in-script&callback=myFunc>

However, the new sheets have a URL like this:
<https://docs.google.com/spreadsheets/d/SOME-IDENTIFIER/pubhtml>

Using "SOME-IDENTIFIER" in place of the key does not work, I'm not sure how I can pull the JSON feed from a new spreadsheet... Anyone have any experience with this?