I mostly had music turned off on the drive home, to listen for squeaks and rattles, but when I got home I sat in the driveway and listened to music and I'll say that yeah, the sound system was a tad disappointing. The subwoofer seemed to be missing? Like low bass was just not there. The rest was OK, but not great. I'd compare it to post-Samsung harman/kardon car audio - it's OK, maybe B-, but you really expect it to be better.
I switched to "Advance" software updates and I'm really hoping that newer builds give the improvement that others have noted. The 2018 Model S had better sound.