Hi Charles,
I haven't used the iPhono but I do have the Graham slee jazz club which offers RIAA settings throughout the years. It really does make a difference. Some of the older recordings including some of the brand-new recordings that are out there aren't even close to the RIAA standard.
With the flip of the switch a dull and muffled recording now sounds pretty good. I think it would be a worthwhile addition for all phono stages to have this option.
… Just my two cents
