here are my jumbled thoughts from having created something similar on our intranet.
we have our calendar broken out many different ways. I guess the best way to summarize is similar to the group forum functionality of v2.0
if you are part of a group and that group has a calendar, then you get all the dates for that group as well as your personal ones. We have the calendar setup much like the outlook style look and feel with a small numerical calendar in the top right corner, with dates that have details bolded, and then a listing of the day you click on
your personal appt are shown in black, then the first groups is shown in blue, second in red, thirs in green
using a color coded chart on bottom
Green * = group 1
and it's viewing is turned on/off using your profile, but we have M$ style buttons in the top of the floated window, the minimize/close style buttons.
It seems to have worked very well sofar anyhow. Can't really give a stress test, it's not used all that often, since 99.99999% have outlook installed already they use that