So I stumbled across a post by Michael Kaplan that mentioned something about text rendering in WinFX:
And two thoughts struck me: “Yay, they fixed Graphics.MeasureString” and “what?! why didn't they fix Graphics.MeasureString?” Well, no, they didn't fix Graphics.MeasureString and DrawString, as that might break .NET 1.0 and 1.1 apps that are already in the wild. So they provided the new (and hopefully correct) functionality in the TextRenderer class. I guess that makes sense.
It also looks like TextRenderer uses GDI to render the text, as opposed to Graphics using GDI+. Arg! Fix GDI+!