Probably about time I replied... and the answer is, I can't honestly remember when the last time was that I stuck something in it!
I do have a temperature sensor gadget I bought on Kickstarter many years ago that I'll not be able to use anymore, but I haven't used it in the last year as it is! I think that says something. I have a bluetooth speaker that alternates between my mac and iPhone 6s, and Beats wireless headphones that I've been using with my iPhone since Christmas.
I understand a very very small group of users will have problems with high quality headphones that cost a lot of money to replace, but switching to a digital connection instead of the analog one currently in use would seem to fit the description of high quality headphones. That said, I'd rather the lightning connector was replaced with a USB-C port for all, as that's a tiny but fast port.