strumming it now, and speaking of "jazzing it up," I guess I tend to go to major 7, and augmented 7, and ninth chords all through the song when I can... but I have a trained singer who appreciates that... I did fill in for someone with another (mediocre) singer who turned to me in the first verse and told me I was "throwing her off" and to play it straight, harmonically and rhythmically, which made it sound like a country song to me
Yeah. Although the tune follows a basic I-vi-ii-V progression, it certainly benefits from being harmonized in 7th's rather than 3rd's. It gives it a much more uptown, sophisticated sound. Standard chords (harmonized in 3rd's make it sound like a country (or maybe a doo-wop)tune as you observed above.
With regard to the singer who was confused by the harmony, I had commented earlier about the difference between a "female vocalist" and a "chick singer". I think a lot of us have stories like that.