Hello Dave ,
Acoustic Guitars sound very nice , also like what your harmonica playing brought to the song ...
It gave your tune an organic Dylan type of vibe and sound ... regarding the vocals , since I don't sing , I don't generally comment on vocals .
I thought your song was a good listen and as it stands it makes a great little demo ...
I suppose if your open to crit's mine would be these few ...
IMHO, A nice low impact Fender Bass , or an acoustic Bass added to your song would bring it up a notch , also some light percussion in place of drums ...
all the best,
Kenny