1. It's native. Doesn't matter how you package a website, it still uses an HTML/JS/CSS engine to let you interact with it. Jason lets you effectively build a native app without actually building an app. The JSON markup is just an instruction to remote control native elements and native functions directly.

2. it's JSON based, it's meant for interacting with APIs, not a website. Websites don't work well because html/js/css have evolved to become something of monstrosity--which is both good and bad.

3. It assumes session. It assumes that you will be the sole user of the app, which browsers can't do for many reasons. So it has authentication/key management system built in.

4. More coming soon: This is just a first version, I intentionally cut down on many features I could have implemented because I wanted to see what people think first. I have a couple of production apps from which I extracted Jason. For an example check out www.ethan.fm It's running on Jason.