We are a 5-piece band playing Hungarian folk songs with classical rock arrangements (drums, bass, 2 guitars, vocals). Drums are electric, all guitars coming from line, no amps. We use a Soundcraft UI16 for mixing where we can save all our settings.
However, some venues require to provide them not only with L/R outputs but separated vocals, instruments, etc. There comes this fine little unit (we actually have two in our rack to have 16 tracks): mics, instruments go to its input, from one output we go to our mixer, the other, galvanically separated output goes to FOH as required by the venue - and everybody is happy. We can use our usual monitor settings and FOH can be mixed by the local professional sound guy.
Art S8 is built like a tank, it does not color the sounds in any way and just does its job: making two identical signals from one source. It works not only with mics but with line level instruments (Line6 Helix, Yamaha Stomp, Roland TD11 drums) also. We did not regret buying this splitter.