Mac renders fonts optimized for "correctness", which can appear fuzzy at low resolution. Their new hi-res (~200dpi) screens solve the problem, you get correctness and legibility.
Windows and Linux tend to optimize for screen legibility at low resolution, resulting in increased sharpness. At hi-res, they'll likely not look as correct as the Mac rendering.
Mac renders fonts optimized for "correctness", which can appear fuzzy at low resolution. Their new hi-res (~200dpi) screens solve the problem, you get correctness and legibility.
Windows and Linux tend to optimize for screen legibility at low resolution, resulting in increased sharpness. At hi-res, they'll likely not look as correct as the Mac rendering.