This somehow reminds me of Inception. We have a perfectly functional computer, then we run a browser on it, we download a bunch of HTML, which in turn will download a whole slew of JavaScript in order to create the illusion of an application running natively that offers a subset of what the computer could offer. The only difference is that this web application supposedly runs on 'all devices' except that every web application is quite brittle once you try to actually run it on all devices. And forget about device access (though that is slowly getting a bit better).

The only plus I see in all this is that in the end we are now free of the API lock-in that OS vendors traditionally required, that we tend to take 'client-server' applications more or less for granted and that because it is server centric you don't have to bug your users to download the latest version every time you improve things (though as was pointed out in another thread, this is also a disadvantage, as a user you lose control and if the company goes out of business you could lose it all).

The web also roams much easier.

If we keep going like this for a little while then we're back where we started, with the graphics terminals from the 80's, (canvas is pretty close actually) only this time across the WAN instead of a lan and with the ability to hyperlink between applications.