One of the big unresolved questions is how to distribute this thing — it’s what’s called a “binary rendering behavior” in IE parlance, and is packaged as an ActiveX component (well, it might or might not be ActiveX — I don’t really understand that part of the equation). Currently, the experience is pretty crappy: you have to click through an infobar to allow installation of this component, then you have to click “Yes” to say that you really want to run the native content, and then you have to click “Yes” again to allow the component to interact with content on the page. This sucks. In theory, with the right signatures, the right security class implementations, some eye of newt, and a pinch of garlic, it’s possible to get things down to a one-time install which would make the component available everywhere.
Mozilla is now paying people to fix IE, in this case canvas support.