I use Google Calendar and attend a few Meetups, and when I RSVP to a Meetup event, Gmail automatically makes an entry in my calendar for the Meetup from the notification email meetup sends. And keeps it updated, and that is really nice.
But... I've noticed that people I share my calendar with, like my wife, kids, and a few friends, can't see those events. They think I'm free that evening, when I'm not. That's (really) bad, because I depend on Google Calendar to keep us all on the same page.