Even on a screen with not-particularly-high DPI, grayscale AA is fine. Subpixel AA was a brilliant idea for the displays of 2005 (72-96 DPI), but it came with lots of downsides (like color fringing on dark backgrounds, or for users with astigmatism). Grayscale AA drops both the benefits and the drawbacks, but even at like 100 DPI, the difference is very marginal.
At 110 DPI (27 inch 1440p) it's not that marginal for me. Even looking somewhat closely the difference is quite obvious. Subpixel AA is much more readable if the font size is small, and still looks sharper for most interface fonts.
Color fringing on dark backgrounds is yet another artifact of anti-aliasing being done with a misconfigured gamma. Regardless you can configure subpixel rendering to minimize these fringing effects.
