Some use cases of the mouse wheel doesn't work well with inertia, so developers should have the ability to detect whether a mousewheel event is generated by inertial scrolling or the user actually is manipulating mousewheels. I suggest adding a isInertial (webkitIsInertial?) boolean flag to each mousewheel event, so it will not interfere current applications (much like how webkitDirectionInvertedFromDevice is done).
Some use cases include: Google calendar changing month, Google Maps zooming, Paging scrollviews etc.
This needs to be discussed in a standards group, like WHAT-WG