I've been a big fan of Homekit for the past year. It works really well for the most part, and I've had very few problems... until two days ago.
My Yale door lock malfunctioned and I was sent a new lock. I went into the Yale app with the intention of removing the previous lock from the system. Well, one thing led to another and because of some confusingly-worded UI I ended up DELETING MY ENTIRE SYSTEM. I went into the Home app and everything was gone.
Part of the blame goes to me for not being careful enough. But I place a huge portion of the blame on Apple for giving a third party app the ability to even do this. And of course I blame Yale for choosing to make that possible. I have no idea why a door lock app would need this level of access to Homekit. It's baffling. And I'd be just as pissed if I was able to do this from the Hue or Lutron or any other apps with access to Homekit.
After a call to Apple, they suggested I try wiping my phone and trying a restore of that morning's iCloud backup, which includes Home data! Hooray! ...except it doesn't work. Like, at all. I went through the annoying process of wiping and restoring my phone, and when I opened the Home app it wouldn't even load the data. It eventually did, but none of the devices showed as responding. Then after a couple minutes it all just disappeared.
Long story short-ish, after several other calls to Apple, a support rep started leading me down a path where I basically said "so you're having me re-setup my Home system, aren't you?" They had no idea how to fix it so I had to start over from nearly scratch.
If you get into Homekit: be careful.
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Matt