if (chrome.app && chrome.app.isInstalled) {
...
You're right.
> do u have any public stats about the chrome web store?
No I don't.
> and is there a way to retrieve the number of users of a chrome web app
> solely client side?
You can use the technique above to record visitors that are using your
site in Chrome's app mode. You'll still have to send this data to a
server and aggregate it, though.
HTH,
- a