@aeva I just did a quick test. I spun on my chair for a minute while randomly twisting the controller on all axes.
After a minute or so it had drifted maybe 10-15 degrees on the yaw. Not too bad, and I'd expect that since it's most likely only one IMU.

I haven't found out yet what the IR tracking is like. It's supposed to have IR markers so the Steam Frame can see it, that might let an external camera track it for yaw correction.