Finally!
One of the more obvious enhancements in iOS 15.4 for the iPhone is the ability conferred on FaceID which allows unlocking of the phone while wearing a mask. It works well and is very fast, though sadly it’s restricted to iPhone 12 and later. I still stubbornly insist on wearing a mask in the land of SUVs and gun rights, so this is nice to have in the supermarket.
But a relatively unsung enhancement – only 15 years after the introduction of the iPhone – is the added provision of nested mailboxes in Mail, denoted by the arrow. Click the arrowed item and the underlying mailboxes are revealed. For one who adopts fairly structured mail storage methods, this is huge, as my large number of mailboxes has now become quickly accessible, just as on the desktop OS:
Nested mailboxes.
The other very significant enhancement which has gone largely unremarked is the great improvement in voice recognition. For a device with a small screen and a near useless keyboard, the error rate in recognizing spoken words has fallen by an order of magnitude. What was borderline useless is now suddenly quite competent. As an example, I dictated an email with the names of the last six despots ruling the Russkies* and voice recognition got every one right!
iOS 15.4 is a significant improvement, for these issues alone.
* I was making the point that assassination is a remote hope, and that the first five had all died in their beds, and the sixth is likely to. Their leaders may whack subordinates with impunity, but seem to survive just fine.