Fantastical 1.0.2 for Mac supports BusyCal
While I read our review of Fantastical with much enthusiasm, as a longtime BusyCal user I simply couldn't afford to play dice with my calendar. But Fantastical 1.0.2 is now available, and the primary update appears to be that the natural-language calendar tool now plays nice with BusyCal. You can get Fantastical from Flexibits directly or on the Mac App Store.