How does Google take to this? As far as I can tell it has to evaluate the JS before it can crawl the site; I got a few seconds of "Loading..." after the page had finished loading while it was pulling in the JSON.
The best way to circumvent the issue is to prevent the browser from caching the request (ex. cache busting via random querystring parameters), or to use different URLs for the HTML and JSON response (ex. appending '.json' to the end of the path).
How does Google take to this? As far as I can tell it has to evaluate the JS before it can crawl the site; I got a few seconds of "Loading..." after the page had finished loading while it was pulling in the JSON.