If it’s a Catalyst app — which it likely is — they’ve done a fairly okay job. A few flaws I noticed after a couple of minutes of trying it out:
The video experience could (and should) be better. In full screen, videos only fill the window, and if you actually want full screen, you have to take the app to full screen. Even then, the toolbar is there, so you’ll also need to hide the toolbar. What you’d normally achieve on a good Mac app with one click takes four here.
Also, if you don’t hide the toolbar and mouse up to summon the menu bar, the video controls up top, such as close and speed go partially under the toolbar. Maddening.
The Overview text under videos is not selectable. Not the first time this happens on the Mac (or anywhere for that matter) but it still deserves a mention.
There’s no way to copy the URL of any of the stuff — videos, news, events, etc. AirDrop, Messages, Mail, even “Add to Reading List” are all there, but there’s no way to simply copy the link. Even the iPhone app can do it.
This is the app’s first release for macOS, so a few shortcomings here and there are no big deal. But WWDC is next week and I doubt the app will receive any “meaningful” update by then. And hey, we all know unselectable text areas are never going away.