If you head over to Surfin Safari, Webkit’s blog of new features, you’ll find some neat new HTML5 3-D tricks that Safari 4 (including the latest Webkit builds and Mobile Safari on the iPhone) can do without breaking a CPU sweat. We had our doubts (and still do to a degree) but this is the kind of animation that makes Flash seem a little less … "necessary".
In a non-scientific test, running Morphing Power Cubes, the browser used 5% of the CPU. Flash usually starts at around 30% just to be activated. These examples also run incredibly smooth on the iPhone and iPod touch.