(Ejecta dev here)
Ejecta uses OpenGL ES 2 for Canvas, not Core Graphics.
The default demo that comes with Ejecta[1] runs with 60fps on the iPhone4S. Just try it in Mobile Safari. Even Desktop Browsers struggle with this. Of course it's a contrived benchmark, but it still makes a point, I think :)
There are also a lot of other reason to use Ejecta. If you _want_ to distribute your App in the AppStore, the alternative is to use a WebView framework such as PhoneGap, which can't use JIT either. That said, the raw JavaScript performance is rarely the bottleneck for games - most of the time, drawing is.