Doesn't look like it adds much of anything to the Apple calendar, which itself is a pretty minimal implementation. I actually found it worthwhile to pay $50 for Busycal which has a lot of features important to me (presumably not to most people). Fantastical also has a following at around the same price point, though it didn't do it for me.

I wish notion supported the mac, but they just have a lame web view which isn't any better than using a web browser. Doesn't act at all like a native app.