I've read lots of great things about Fantastical and finally bought it. The advantage it has over default Calendars is that it shows Reminders with times inline with calendar events. That's great, but I've also noticed that it's quite laggy when I go from the complication to the native app. That is, I can't scroll for the first few seconds while it refreshes. For me, that's a dealbreaker. The native Calendar app loads up and is responsive right away. The other advantage of Fantastical is you can create events using natural language input, whereas Calendar doesn't let you create an event unless you use Siri. Am I missing any other benefits of Fantastical? because for now I've stopped using it.