It works - unless it doesn't. It seems that some people upgraded fine, but certainly not all of us. I actually didn't intend to take the update since the 5s is "older". Unfortunately, I woke up Friday morning to find that my phone had begun the update, but hadn't finished. After 2 hours of trying to give it plenty of time to finish, I ran searches on the web and determined a restart was in order. That didn't fix it. I went to my nearest Apple store and spent an hour with them. We thought they had me on my way and I brought my phone home to restore from backup (which fortunately was only 1 week old). Unfortunately, the restore also hung/froze/never finished. I let it run all night long and it never finished. I returned to the Apple store where I spent 30 minutes waiting to see someone and...I wish I was exaggerating about this next part, but I'm not...I spent another 5 hours getting help that didn't ever fix my phone. It was 5 hours of update retries and restore retries (I had my laptop with me). I was there so long that the tech guy helping me went on 15 minute break once and later took his lunch (and returned). Each update retry and each restore retry took FOREVER and never would finish (just like the first time). Eventually, I left with a new iPhone 5s (a loaner if you will because my intent is to get a new phone very soon on black Friday) and instructions from them on how to finish the process of restoring from backup at home. Unfortunately, I had to return to the store because that also didn't work and in fact, itunes gave me a message that it couldn't find the iPhone at all. When I returned to the store they determined that it must have been a "dud" and so gave me yet another one. My plan was to buy an iPhone 8 on black Friday. However, given that it was Apple's own iOS update that broke/bricked my iPhone 5s, I've decided to do some phone research before sticking with Apple for another go-round. Also, my research has uncovered that it's not that uncommon for ios updates to brick an older phone and falls under what many are calling "planned obsolescence". I recommend that you NOT update a 5s to ios 11 or later. It's just too risky and it ***** being without your phone (unless you have more than 1). I also recommend researching how to get rid of the nag screen that will continually ask you to update.