That view was understandable - the problem I've ran into recently is that canvas rendering on mobile can be quite slow. I found this when I started porting The Crate Flood from ActionScript over to TypeScript and tried it out as a PhoneGap app. The canvas rendering times seemed poor (using a Sony Xperia P with stock browser):
|The Crate Flood on HTML5 Canvas|
|The Crate Flood with a debug GUI, debug console and performance stats|
It looks like in the past few years things have changed with regard to rendering performance. The Turbulenz engine and other trailblazers utilize a WebGL renderer for high performance rendering. They also use TypeScript to create a more maintainable and reliable games engine. Furthermore, Microsoft have delivered a build of Internet Explorer 11 in the Windows 8.1 preview that implements a good chunk of WebGL functionality.