I made this just as a general info for those uniformed.
It is simplified, but generally speaking these are main possible paths with default settings.
X axis is market share (with some guessing).
I know a small examples of renderings could be included for better understanding, and I will post this & other refinements later.
A few things not mentioned:
Linux with FreeType rendering, but I have no idea how many people use subpixel rendering or other settings. Each setting has probably less than 1% of users.
Quartz rendering does also other types than subpixel AA, but I would say they are in minority (I really don't know).
There is also an old version of Safari, with Quartz rendering on Windows with default setting.
Mobile market falls under Other, but some browsers aren't capable of displaying @font-face fonts anyway.
PS: I made this quickly, I hope there is no huge mistake that I can not see...
[edit: I made corrections and some changes. Old version is attached below.]