The iPhone 6 was the most successful iPhone that was ever sold, and accomplished this by a healthy margin over the previous iPhone within a few short months of it's release. As a phone, the iPhone 6 is fantastic, is a very well made piece of hardware, and doesn't appear to suffer any of the design flaws that sometimes plagued previous models.
Unfortunately, the iPhone 6 has one big design flaw that can cause the phone to stop working completely, and as I write this, there is still no known solution to the issue. The problem is related to the iPhone 6 home button, which contains the 'Touch ID' fingerprint scanner. If your iPhone 6 home button gets damaged and stops working, it is essential that you do not attempt to update your firmware, as it will render the broken iPhone 6 unusable. Even if you get the iPhone 6 home button replaced, you still cannot update firmware, as it will cause the same issue to occur.
Thankfully, once you're made aware of this issue, it can be avoided, like the customer who's iPhone 6 is featured here. If you do have a damaged iPhone 6 home button, the iPhone 6 home button replacement can be carried out within a couple of hours, with a full 6 month warranty on the repair.