For me anyway, vocal harmonizers don't replace the real thing. It's one thing to see one person on stage and hear harmony coming from one person. It's a totally different thing to have three folks on stage where you can hear the differences in their voices, see their expressions...hear the natural sound of harmony that way.
For me, vocal harmonizers just add interest to the song when I'm playing solo. Nice to have something a bit different at times rather than just the melody...sort of like changing keys in a song now and then.
guitpic ... I wholeheartedly agree ... a VH unit compared to two/three/four or more part LIVE harmony is analogous to an arranger keyboard being compared to a two/three/four or more piece live band ... there is no comparison, but absent the availability of LIVE singers and players, I have to appreciate the fact that I have a VH unit and a KB to work with ...
And I know all the arguments against working with a band, so I don't have to hear them again, but I will repeat, that working with the same 4 guys for 26 years is something I will never be able to replace ...