While interesting, it has a number of drawbacks that make it far less interesting than the HTML5-based approach that works in the standards-compliant browsers based on WebKit, Gecko and Opera, as well as the improved IE8.
First of all, it has to bootstrap .NET into Firefox (or whichever browser you are running it in). This adds a few milliseconds to your page’s cold load time if it’s not already loaded. In the day and age of fast websites, any additional page time is just a no-go.
One of the other claims about Gestalt is that it preserves the integrity of “View Source”. I’d argue that View Source is dead – and it has been for some time now. I rarely trust the View Source representation of the page.The web is still open, but it’s more about inspecting elements and runtime styles and being able to tweak those. I rarely trust the View Source representation of the page. Dynamic DOM manipulation has all but obsoleted it. Firebug provides this for Firefox, while Chrome and Safari come with an advanced set of developer tools out of the box. Even IE8 provides a basic, though buggy set of inspection tools.
The last unfortunate point for the Gestalt project is that it requires a plugin installation on Windows and Mac, and is effectively unsupported under Linux. You won’t see any of these Gestalt apps running on an iPhone or Android device any time soon either.
So where do I see the right path? HTML5 as a platform is powerful. Between <canvas>, SVG, and HTML5 <video> you get virtually the same rendering power as the XAML underlying Gestalt, but a significantly larger reach.