BusyCal is everything that iCal should have been. I’ve been using it for over a week and I love it. I can tag notes, calendar entries, and reminders. I can also sync easily with other users’ calendars and Gmail. The ability to put sticky notes each day to remind yourself to complete certain tasks is brilliant.
The best features are the most trivial, perhaps, but I love how BusyCal shows the weather in my city and the phases of the moon. It has so many other cool features that you’ll just have to play around with it.