Given that they managed to break volume control for iPhone 7 users like me (other versions too?), this isn't surprising in the least. Volume control mostly works now (11.0.3). However, half the time now it'll show the volume changing, but the actual audio output will be unchanged (may be an app issue, happens mostly with WhatsApp voice calls, but have had it happen some with the built-in Music app, not as reliably flawed there).

I'm still rebooting every couple days to keep bluetooth working reliably with my car. Maybe by 11.1 I can tell my sister and parents that it's safe to upgrade.