In this particular case there are issues like the lack of anti-aliasing for border-radius and hardware acceleration prior to 3.x. Also while this isn't strictl

In this particular case there are issues like the lack of anti-aliasing for border-radius and hardware acceleration prior to 3.x. Also while this isn't strictly the same thing, there's a lot more to the browser than just the way the DOM is rendered. The way many of the different browser APIs behave between implementations is drastically different. Off the top of my head orientationchange events, xhr with app cache, (replace|push)State, touch events, and the list goes on.