We are heavily using it in production on http://casinorpg.com (not a common use-case, but it works well for us). Basically, when a player creates a new character, they are able to customize out of millions of unique possibilities. Since the game is HTML5, we must generate a unique PNG sprite for their character. We run Manta jobs to do this by generating the image, compressing it and then storing it directly in Manta (where it then gets picked up by a CDN).