For me, mature tank with real live rock and sand. Ich tomont stands no chance with all of the critters on the surfaces of my tank - free meals. I am under no illusion that this is eradication, but I learned long ago that this is mostly a pipe dream for nearly all and that I would never be one of the otherwise... just not intent on QTing every invert, coral, rock, etc... and something is going to slip by for nearly everybody and especially me.
I do isolate fish when I get them, make sure that they are not skittish and eating everything... then into the large tanks they go.
I would never do this since it is not responsible, but if you put an ich covered Powder Blue Tang in my tank, there would be nary a spot on any of the other fish...and if there was, it would soon be gone never to be seen again. I have no idea if the PBT would make it, but the healthy fish would be fine.
All of the people who start with sterile tanks with bare bottom, dead/dry rock, etc. are creating a perfect petri dish for fish disease. Yet another thing that the proponents of dead/dry rock tend to leave out.