Ashley, 
Joannesalfa : CSS 3D transform are indeed hardware accelerated on iOS. However, you must be careful with them, because WebKit falls back to CPU when you mixed them with other DOM transform, it depends.
For example, text & box shadow makes everything back to the CPU.If the 3D transform is performed alone, everything is fine, but if the transform is performed over another transform, there's a performance hit, and so on...
However, it's pretty easy to hardware accelerate any transform, when it's possible.
If you just add
-webkit-transform: translateZ(0);
to your CSS transform, even if that transform doesn't do anything, the matrix transformation involved activate the hardware acceleration.
So, if you want to accelerate the transform applied to a div, you simply need to do that in your CSS:
div {
-webkit-transform : translateZ(0);
-o-transform : translateZ(0);
-moz-transform : translateZ(0);
transform : translateZ(0);
}