Google Calendars are up and running but, as with a few other Google services, I've had some issues in my first few minutes of testing it with OmniWeb. I got GCalendars to work if I spoofed as IE for Windows. Unfortunately, FireFox for Mac doesn't do the trick in GCalendars and IE doesn't do the trick for GMail. I did successfully import one calendar in from iCal. Well, 95% success. I got 89 of 94 events in. I don't have time right now to find which events failed and why. After import, I had an error window pop up which declared an Undefined Value error occurred and contained mostly gibberish that looked like my iCal calendar export interpreted as text. A similar window popped up when I went to view the calendar but those were the only two occurrences for me and things did settle down and work properly after that.
You can be certain I'll be testing GCalendars more when I have some time. I even sent out an invitation. If only I could set different preferences for mail.google.com and
www.google.com/calendar