I have just been playing with the calendar and experimenting with the categories option.
The problem I find here is that if you have a large Moodle installation with many layers of categories etc. then selecting this option is pretty insane. I know what the idea is behind it, that being to help with sharing things over two or three courses, but here thrying to find the courses to share with when you have several hundered categories is not particularly practical.
Would there be a way to somehow limit the number of categories displayed?