To test the inclinometer, for instance, Gizmodo downloaded a level app to the iPhone 5s, then placed it flush against an actual level, which showed a 2 degree level of inaccuracy.
And in testing the phone’s gyroscope on a level table, the iPhone 5 recorded it accurately while the iPhone 5s measured it as -3 degrees off level. This can have a serious effect on gaming, and a test running Real Racing 3 shows the car steering left when held against a level table.
There isn’t a level on hand in GigaOM’s New York office, otherwise I’d test it out now myself. But there’s no doubt that the motion sensors are inaccurate on at least some of the iPhone 5s models out there. Depending on how widespread this is, and whether this is a software or hardware problem, Apple could potentially address the affected phones with a software update or calibration tool and tweak the production of future iPhone 5s models.
Until then, best to break out the real level when it’s time to do your next home renovation project.