Certainly cool that Google is working on this. I suspect someday it will all work perfectly.
However, from working with customers of BromBone, I know this. People have javascript powered webpages that were not getting indexed by Google. Google would crawl the page, and see no content. The pages were not in Google. After creating prerendered snapshots and serving them when the _escaped_fragment_ parameter was present, the pages showed up in Google.
