[pavlov]

Like you say, 3D matrix transforms are already included in the low-level graphics APIs that are increasingly being used to accelerate element compositing in modern browsers. So why not make this functionality available to web content creators through CSS?

When you're on the GPU, rendering a quad with plain old scale+translate is just as fast as rendering it with a full 3D transform (with the important twist of potentially increased texture sampling and edge antialiasing requirements, of course).