Impact for iOS
I know you're waiting for the release of the Impact Game Engine, and I promise you, it's coming. I just get distracted too easily. So here's my game Biolab Disaster running on the iPhone 3GS with 60 frames per second:
The game is running in its own process and is not using the iPhone's browser at all. Instead, it's just using the JavaScriptCore Framework to run the game. All the necessary calls to the Canvas API have been reimplemented with OpenGL-ES and the touch input is passed over to JavaScript to be evaluated by the engine. I of course had to make some changes to the engine, but the game source code is exactly the same as for the web version.
The JavaScriptCore Framework is still private on iOS. So as it is now, I won't be allowed to distribute the game in the AppStore. But my understanding is, that if I bundle my own copy of the JavaScriptCore Framework (which is part of WebKit and thus freely available) with my game, I should be on the safe side. Let's see how this works out.