eric - good stuff. I have a lot of comments - feel free to ignore them all; they're probably wrong.
I really like the song. Nice laid back feel, the chord progression and the harmonies definitely have a retro feel, but the lyrics are very up to date (and very well written).
I really like your lead vocal style - urgent, edgy, breathy, cool. Liked the wee "extra" vocal bits too.
I think there are two directions you could go with the backing vocals:
1. Really tighten them up in pitch and timing - lots of takes, comp together the best, Autotune, etc.
2. Double or triple track each part, don't worry too much about exact pitching or timing, and put them "back" a bit in the mix. Make it sound like a whole room full of people singing sort of together.
I think 2 would be cooler.
Acoustic - nice playing. Too loud, and it's clashing with the vocals sometimes. Compress and roll off some (more) lows on the guitars. Put them in some space. By the way, loved the harmonics.
Also, compress the hell out of the lead vocal (not the bvs). The levels vary too much just now.
Bass - too boomy. Sculpt some space above and below with some EQ. Make the sound a bit more "punchy" and defined. Also, leave some space in the playing itself - try a bit more of a "McCartney" feel with shorter, almost stacatto notes with space between them. Steal some of macle's bass ideas. Hell, steal as many of macle's ideas as you can - I know I intend to.
Drums - loops can be cool. They should be louder. Play some real drums on top - you're a great player, let's hear it!
Loved the "whistling" sounding synth. Turn it up a wee bit.
Hope this is useful. I really like the song, and I think you should preserve the loose, laid back feel. It's very cool.
Cheers
AB