I'm having no problem hitting 8" - 10" deep clad coins in my test garden with good audio but the VDI is jumpy at that depth.
I had it out in the woods yesterday and dug a bunch of shotgun shells between 7" - 9" deep running at with max sensitivity in field mode. I pulled an old brass coat hook that was well over 10" deep with solid VDI and tone.
There are a few things I don't like about the Simplex but the depth is outstanding. It goes a bit deeper than my T2se and Xterra which is all I have to compare it to at the moment. If I run the T2 in boost mode it has about the same depth as the Simplex.
It's turning out to be a great relic hunter so far. I haven't tested it in water yet and probably won't be able to until late spring.