[gehsty]

There are edge use cases, I think 99% of the time your interaction will have less friction and more security.

For the edge cases generally a pass code will work (under the table / multiple users). I'm not sure what you do with your phone unlocked in your pocket...

TouchID being quicker is your opinion, and as neither of us (I assume) have used it, we'll see if it is quicker.

I just think there were lots of negativity about TouchID when it was announced, and look how successful that is, would Apple risk that success? I don't think so...

[dogma1138]

Edge cases are the most important ones to consider when talking about usability since all other cases are irrelevant.

[gehsty]

The least used interactions are the most important? Really?

I would say the opposite, the interactions that the most users use the most often are the most important.

[dogma1138]

Edge cases are not the least used interactions, and even if they are it's not what makes them edge cases.

Edge cases are defined as what happens at the edge of operating parameters the classic example of a speaker that is played at the bottom or top 10% of it's output, edge cases do not have an intrinsic definition of occurrence rarity. It might not relevant to you, but if you like blowing up your house with all that bass or you have very thin walls and you have to listen to music very quietly then these are still edge cases but they are not rare cases for you.

In reality and in practice edge cases are pretty much anything that goes out of the (pretty narrow) definition of how a device or a service should be used (the classical remark of "you are holding the iphone wrong" comes to mind).

On your daily usability the edge cases are also much more important for the general satisfaction and subjective usability values of the device. When you are in a perfect position/condition to use your phone the environmental conditions overcome any design flaws, and you experience pretty normal usability.

When you say hold the phone on the floor by your bed to avoid the light creeping all over the room, under the table during a meeting, or as close to the floor when possible at a theater is when the flaws in usability start being apparent. That's when things like the placement of the fingerprint reader (or lack there of), weight, size, screen readability at low brightness and odd angles start to become more and more relevant.

Same goes for other things, you don't care about how much leg room there is in the back of your car until you need to fit 5 people over the weekend, despite you using it more times solo during the work week.

[gehsty]

I still fail to see how it is not possible to unlock with your passcode for the two use cases you mention.

I think I understand the point you are getting at, design for tricky situations and the normal situations will be easier, but I think you are failing to see that you cannot design for every scenario, eventually you have to weigh up the feature sets of two technologies and pick the best one for most use cases and users, which Apple obviously thinks is FaceID.

I think FaceID will allow features simply not possible with TouchID, and expand across the Apple product line, and to other manufacturers, to the point where in 5-10yrs time we just expect screens to recognise us. This is an important step towards this.