Late to the party but,

I wish there was a way to have "named" constraints that you voukd share between tables. Because they would behave akin to mixins and that would open up a world of possibilities.

(And if you're into that sort of thing, there's a lot of type theory concepts that could be applied on top of it that would make things much more practical and approachable)

Also, I'm eagerly waiting for Incremental View Maintenance to be merged into main postgres.