hi,
i´m use a MADI system (iLive-MADI Card and RME-MADI HDSP Card).
it is very simple to play the channels from a recorded show back in the iLive.
i´m used “virtual soundcheck” in different situations.
my opinion: this ist not a “must-have”.
the problem: you have no original-sound from the stage. the sound from the backline is missing!
but, somtimes, it can help to estimate the sound of unknown wedges or so…
or in big stadium-situations, where the backline ist not loud enough 
