Barely used as I have (had) too many other headphones.

User replaceable Li-ion battery should be in excellent condition, it seems to hold its charge in line with the manufacturer specs.

Original kickstarter bundle:

The world’s first wireless headphone with a high-bandwidth Bluetooth audio codec, a THX AAA™ amplifier, and phase-correct planar-ribbon drivers (a combination we call the 3P Signal Path), Panda puts you closer to your music than ever before—wherever life takes you.