From the patch announcement by Dan Luedtke, "This patch introduces the Lanyard Filesystem (LanyFS), a filesystem for highly mobile and removable storage devices." The kernel patch then goes on to describe Lanyard FS as "The lanyard file system (LanyFS) is designed for removable storage devices, particularly those small gadgets one would carry around using a lanyard."
In a follow-up message by Dan, he describes the big feature of LanyFS as having not many features. "That's the feature, actually. Think of the Arduino platform or other embedded devices (TV, Car Entertainment) that just want to read/play files. You're right, no big features, but that's by design."
In another message self-described benefits include simplicity, interoperability, and flexibility. Mentions cons though include LanyFS being feature-less, use of recursion, a max block size of 4k, and no use of MTD/UBI features.
The Lanyard File-System work for Linux is currently in a "request for comments" stage although it looks like initially not all developers are excited about seeing this file-system.