I'd note that when moving from pg to $other the thing that really trips me up isn't the syntax changes, it's the lack of ARRAY and ROWTYPE.
I'm not sure whether those are in scope for you but it'd be nice if the docs said "to be implemented" or "out of scope" somewhere ... and my apologies in advance if they do and I somehow missed it.
We already have support for LIST and STRUCT (which I think are equivalent to ARRAY and ROW, respectively). There is still some functionality missing there (notably storage, and several functions) - but the base functionality is there and the remainder definitely will be added.
I'm not sure whether those are in scope for you but it'd be nice if the docs said "to be implemented" or "out of scope" somewhere ... and my apologies in advance if they do and I somehow missed it.