A while ago I reported issues around the Mustang subpixel AA.
The differences between the Mustang rasterizer and MS Cleartype
are still significant for the Windows default control fonts with build 91.

There are two types of problems:
1) some Segoe UI glyphs look significantly different, e.g. 'e', 'a',
 's', 'c', 't'
 
   changing the whole character and style of this great font. See
   http://www.jgoodies.com/vista/segoe-ui-comparison.png

2) The Mustang subpixel AA rasterizer doesn't scale the font weight
   (thickness of glyph lines) with the font size. Cleartype scales well,
   where Mustang seems to use integer metrics. Here's Cleartype:
      http://www.jgoodies.com/vista/segoe-ui-wordpad.png
   compared to Mustang:
      http://www.jgoodies.com/vista/segoe-ui-mustangb87.png

I would like to point developers and Sun folks to these issues.
And I couldn't find these issues in the bug database. I'm aware of
6438263 "Need to handle new TrueType 'gasp' table version in vista fonts",
4924220 (fixed) "Need to handle new TrueType 'gasp' table version in
vista fonts",
and 6282527 "LCD text artifacts due to T2K (font rasteriser) scan
conversion of contour to glyph image"
But none of them seems to describe the above types 1 and 2.