No I've never heard the demo, really can't be bothered with them generally. There is plenty of legally released FM related stuff that I never get time to listen to as it is.
While the rest of you are listening to Stevie demos I'm listening to Brunning Sunflower Blues Band, Danny Kirwan, Savoy Brown or Billy Burnette (to name a few)
As for the SYW version of Smile at You, I really like the song, it is one of the better songs on SYW (though to be honest I can only fault the last two tracks on the album anyway).