I use a voice live play, and so does the singer (after using mine). Good echos, good harmonizing if you set it up well (certainly worth you making presets for songs knowing what the key is). Had a few glitches with mine though, but it is underpowered on a pedalboard, so probably why.
My wife has the Mic Mechanic, it adds a bit of warmth, but more an individual singer thing, as it doesn't do much that you couldn't do with the mixer (or it does, but probably not enough to warrant). I have just got a TC Critical mass as I realised that for mostly backing vocals, all I really need is the gang vocal and backing singer stuff. Its also smaller and space on the pedal board is a big thing for me.