well, i have one steel string on my acoustic right now because one string broke and that was the only replacement i had. It sounds ok. sounds brighter than the bronze strings. but the one i have on it is a D string, so its wound and might work better on an acoustic then say a high e steel string.

I did that in my early guitar days. Finally I decided that bronze just sounds richer on an acoustic.

A couple of years ago I saw a guitarist playing with bronze strings on a hollowbody jazzguitar. That sounded good. I guess it emphasized the acoustic qualities of the guitar.

Depends on the pickups, too.

Michael Hedges had an amazing acoustic tone, and he used nickel-wound steel strings on 'Barbara,' his Martin acoustic. But, then, he had a magnetic pickup in her, so that helped. I use steel strings on my Ovation acoustic, because I prefer the sound. The bronze strings are richer, steel is brighter. You can also get copper, gold, silk, silver, and just about any other kind of string imaginable.