As Long Zheng found out, though, ClearType as a whole isn't missing - only its most defining feature is not available: subpixel RGB optimisation. This technique uses the subpixels in LCD displays to improve glyph rendering, but by using only the red, green, and blue subpixels, this causes the edges of characters to display tiny coloured fringes. Some people find these coloured fringes incredibly annoying.
Without this technique, ClearType is reduced to more basic grayscale rendering, which produces - in my view - sub-optimal rendering. However, unlike what I initially assumed, this is not the same as the kind of shape-accurate rendering Apple employs.
Where's your bits on the differential display on tablets vs. everything else? Is there going to be a W8 tablet edition?