So in essence it's a lot of work for a small functionality gain?

There are some things that are inconvenient to do without window functions, but my primary use for them is simple optimization. Most of the cases where I've used window function in postgres, the query would be trivial to rewrite to use a subquery instead. Window functions always led to a much faster query that scaled much better over large query sets.

Exactly why I miss them so much.

Reading through the responses just screams: not worth the effort. I know it’s an open source volunteer product and even with a commercial arm the lack of window functions (aren’t they part of the SQL standard?) is laughable.