I ran the same image through Smush.it and through jpegoptim. Smush.it saved 8.46% whereas jpegoptim saved 8.01%. The minimal sample size makes this very anecdotal, but it looks like Smush.it has interesting performance. But without an API, this service will remain a gadget and users will stick to their scriptable tools that don't cost them a network round-trip and a manipulation by an untrusted third-party. - Jean-Marc Liotier from FriendFeed MT Plugin