And on a large document it is a lot less usable currently, not just within the document but the interface to, seemed quiet snappy on a short document, IE and FF

And on a large document it is a lot less usable currently, not just within the document but the interface to, seemed quiet snappy on a short document, IE and FF seem about the same, bit faster in chrome (about the usual amount). I'm surprised their not using this to push silverlight actually, seems like a good way to prove it's worth.