Matthew Panzarino went hands-on with the feature for TechCrunch:
In the end, it’s clearly an experimental mode. There are glitches and screw-ups here and there. But overall it straight up works — displaying the power of Apple’s fully armed and operational camera and silicon teams. It’s clear that Apple’s camera team is really pushing the silicon in the iPhone 7 to its limits. The effect is stunning when it works, and continued use makes the device run warmer to the touch, especially on the top where Apple’s A10 processor sits.
Great story, with lots of great sample images. This is the kind of stuff that makes me want to upgrade my phone every year. It should be noted that this feature was made available today as part of the iOS 10.1 developer beta; Panzarino reports it'll be included in this Friday's public beta.
See also: Jason Snell's take on the feature.