I just upgraded to mountain lion. I cannot reduce the size of ical to fit with mail on my 15" macbook pro. In checking around, the new calendar does not allow us to size the window as we want. This is a big miss for apple. we need to be able to size windows as we see fit. also, in lion, and now mountain lion, we only have the option of the stupid fake-leather looking calendar. We should have options for this, too.
Please let me know if there is a fix for sizing the ical window as we previously had in lion. Apple, if you are listening, go for simplicity and flexibility. Let us decide window sizes, look, and anything else.