Why did they need to propose the name filter: for the property? Old versions of IE (5.5ish to 8) supported a filter-property that was hooking into DirectX to do something similar, but by no means identical.

filter: is still used for the various PNG fixes out there.

This is going to cause endless issues and confusion and I just hope IE copes with a filter: it doesn't understand or we will be back to browser-sniffing and serving different markup to different browsers.