The thing that holds many web UI's back is the web/html DOM and the respective CSS recalculations. You get get close to 1000x performance on web apps if you make sure the DOM will never cause a UI block or re-computation on the layout. The web is great for simple apps but if you're building anything complex you have to play a bunch of tricks to get web UI to work. Going full GPU and building your own controls is certainly possible but I'm hoping there's a middle ground.