It's mostly a triumph of design. The Rift's standard headphones sound fine, but as an on-ear solution, they're subject to noise pollution. In-ear headphones are simply more isolating, blocking more outside noise and lending a more immersive experience to VR by default -- which make the Oculus Earphones perfect for Rift users looking for a more intimate sound experience. I took a pair to the Superhot demo booth at Oculus Connect 3 (Oculus is giving a pair to every attendee), and convinced the developers to let me install them on the demo station's Rift. Installation is easy -- a single screw holds each headphone in place, which snap on with magnetic connectors.
The earbuds look a little silly dangling off of the bottom of a Rift headset, but they sound great -- the soft silicone earbuds fit comfortably in my ears, and blocked out almost all outside noise. It was perfect for the VR experience, but a little detrimental to the demo experience: every time Superhot's developer tapped me on the shoulder to get my attention, I jumped. I had no idea he was even there! The buds were quite loud, too; we had to reduce the game's volume by about half before I was comfortable.
As great as the Oculus Rift Earphones sound, they do present one problem -- they're a very personal audio device. Yes, earbuds sound great, but they're also one of the few peripherals we put inside a part of our body. Unless you're comfortable sharing earwax with strangers, it makes the Rift unshareable. Still, if you're the only person in your household who uses the Rift (or you don't mind uninstalling them for other users), they could be a great accessory.