This article was brought to my attention:
http://www.reidreviews.com/reidreviews/
(SEE ARTICLES AT BOTTOM OF PAGE, “A Side Note on Macintosh Computers and Text Readability” and “Zooming Reid Reviews With Macintosh OSX”)
So I turned to my favorite type guru for his expert opinion, Steve Matteson, Ascender, Corp. He was gracious enough to answer and allow me to post his response:
“Hi Nancy,
Boy you’ve really stepped in it with this one! :-) The skinny on this
link is that type on screen is truly a big fat mess. There’s a lot of
bad speculation on this blog but a grain of truth. The variation of
rasterizers is much deeper than the author initially suggests.... he
doesn’t even mention Adobe applications which override Apple and
Microsoft rasterizers to display type in their own preferred way
(their rasterizer is called ’CoolType’... don’t ask why).
It’s a terribly subjective topic - some prefer black and white and
others prefer anti-aliased fuzz. Some just need new prescriptions for
their glasses. The arguments against black and white are that it is
too stark. Also that spacing suffers*. The arguments against anti-
aliased (gray scale) is the lack of edge definition. Microsoft Windows
uses ClearType and some people bitterly hate it because they are
sensitive to the color fringing. Microsoft has had independent
research done which quantifies the legibility of ClearType of anti-
aliasing. I think their claims were a 5% improvement in reading
performance with ClearType.
Apple thinks they have the ultimate solution which needs no further
improvement. They are putting no investment that I’m aware of in
refining type quality. Google and Microsoft kill Apple in side by side
comparisons. Being a hardcore Apple fan this is terribly frustrating.
For Microsoft’s part - the ClearType tuner gives you ability to fine
tune your system for the way type renders in non-Adobe apps.

The attachment with the 6 text blocks shows the range in settings. At
least they realize that people see differently. Apple seems to rely
only on Steve Jobs’ personal reading glasses prescription.
The second attachment illustrates the same *exact* font data rendered
with different rasterizers....

just a ’for example’ to prove that different rasterizers draw type
very differently.
*spacing suffers because most applications choose to round high
resolution letter widths to pixels. The effect is sort of randomized
spacing - good at one size but not another. The alternative is to have
perfect spacing on screen which then is potentially/likely different
than print (causing line breaks to occur in different places than on
screen).
Well I hope this helps.... someday I should write this stuff down....
Steve”