[wpm]

The chin gives you a good touch-point for adjusting the angle of the display and the rotation angle of the entire base, without having to worry about touching the screen/screen bezel and getting finger prints on it.

It's also a great place to tack post-it notes.

[space_oddity]

Sticking notes...Not everyone understands how necessary this is for some people

[fdvdf]

No chin can be adjusted fine on basically any other display on the market today.

[kjkjadksj]

You can do that with a regular monitor too

[wpm]

Of course you can, but its nicer with a larger surface area to lever on.

There's a reason ergotron puts handles on many of its monitor mounts.