I recently returned a Garmin Virb 360, which also recorded 4k video and 360 sound. It also did 5.6k video (which is actually 4k x 2 in the new math) but you had to stitch together with a computer.
It was well built (water proof) and generally well though out. It even stabilized the image, which was prettt awesome. But one of the 4 channels of audio was always blank so I returned it. Before returning it I did do a test ride with it. I'll share it here for reference:
I may have to try this new Theta, but I really hope that someone eventually makes a camera that utilizes a larger sensor (1/1.7 vs 1/2.3). When the Q went to the 1/1.7, image quality improved dramatically.