2013 S owner here; I use TuneIn all the time. And Tesla's implementation of it is so buggy it's infuriating, as there is little hope the bugs will ever get fixed, and reliability of TuneIn as implemented by Tesla has gone downhill steadily over the years. Dumb stuff. Forgetting you were listening to a podcast, forgetting you were 1hr 12min 5sec into it. Random but increasingly frequent instances of "Loading failure" for many radio stations and podcasts even when there is plenty of cellular data signal, etc. Service centers don't care ("oh that's software") and the engineers don't seem to care ("Elon wants us writing video games or doing Netflix") and ... well... grumble.
I'd be very disappointed if they started charging for TuneIn and didn't fix the bugs.