During gaming, my only complaint came from the brightness. At 300 nit, the display isn't as bright as it probably should be. Increasing the brightness setting past 80% resulted in highly saturated whites, as did moving up the contrast, so the display was stuck a bit darker than desired. This same problem came up when editing pictures: the contrast and brightness were both slightly less than stellar, making it hard to determine subtle differences in coloring.
For objective testing, there are a lot of sites out there that have test images, but I have found that the best are on the Lagom LCD Monitor Test Pages.
Stepping through the calibration photos and the tests, a few consistent problems became quickly apparent. As we saw in the more subjective testing, contrast and brightness were the biggest problem. The extremes in brightness across a variety of colors were either indistinguishable or not visible. The most severe case is black and white saturation. No adjustment to the brightness or contrast could bring out a difference in the darker blacks or the lighter whites.
The Lagom tests highlighted two other problems with the G218a1: the response time and the viewing angle. On intensive response time tests, ghosting was strongly apparent. Also, on the viewing angle tests, at an angle of roughly 0 degrees with the center of the monitor, colors varied from the top of the screen to the bottom. The discrepancy is not dramatic, but most certainly noticeable. At other angles, the problem was, of course, worse. While the text and images are legible and clear from large angles, they are not totally accurate.
Continue on to some conclusions.