IE9 will also off-load a lot of the graphical processing to the GPU. They can apparently leverage the Vista/Windows 7 graphics sub-system, and thus the GPU, to achieve much better performance for multimedia support. Oh, and it also includes native support for multiple cores. For instance, Chakra will background compile script code on a separate thread and core from the main IE9 process.
Naturally, no discussion in the article about security holes or patches, or anything they've done to make it more robust in that regard.