Dr. Raymond Soneira put a 42mm Apple Watch Edition model through a number of tests and was very impressed by Apple's first OLED display.
He expressed some concern with the reflectance of the sapphire glass that shows double the amount of the Ion-X Sport model. This is apparent when you look at the image provided by DisplayMate at the top of this post.
Results show the display performs much like the iPhone 6, in compliance with Apple's Retina Display classification. Color gamut, color accuracy, the ambient light sensor, display brightness, and reflectance are all discussed in the results.
The strength and scratch-resistance of the displays was not evaluated with the focus on display viewability performance. The primary conclusion is that the Ion-X glass, essentially the same as the Gorilla Glass on most smartphone displays, provides a better and more readable display experience due to reflectance performance.
Dr. Soneira stated that an enhanced sapphire glass will soon be available that provides lower reflectance while maintaining a high level of scratch resistance.