Do postgresql json functions and operators Just Work™ using clojure.java.jdbc + hugsql?

in my experience, yes.

you have to transform maps/vectors to jsonb types either manually or via some clojure.java.jdbc protocol but other than that everything should work fine

Thanks @jonas - if the column type is json (not jsonb), then it would just mean serializing to JSON prior to calling the insert function, I take it?

I'm not quite sure about that. I've only used jsonb. From reading the postgres docs I think jsonb is the suggested type in almost all cases