> X.org 2D acceleration technologies and APIs aren't as mature and fast as Direct2D and DirectWrite in Windows.
This complaint is confused. X is the wrong place for that stuff (the failure of XRender to live up to expectations being a testament to this). The windowing server should be multiplexing GPU buffers and that's it.
Direct2D and DirectWrite are user mode, client side libraries on Windows. (Maybe the author has them confused with the legacy GDI, which lives in the kernel?)
What this should say is that Skia-GL/Ganesh and Cairo-GL, which are the open source Direct2D competitors, are not at performance parity with Direct2D. I've heard this in the past, though I don't know how accurate it is anymore. Thanks to the work of Google, which depends on Skia-GL for Chrome and Android, it's made rapid progress lately. In fact, in my experience, Skia-GL is basically at performance parity with CG::OGL (i.e. the Mac/iOS 2D rendering backend)—so if the Mac is your benchmark, Linux has caught up there, if you use the latest Skia and configure it properly. Very few Linux desktop apps use Skia-GL in practice, though, which is a separate, and unfortunate, issue.
(Finally, I should mention that Direct2D and its competitors constitute a really low bar if you compare to the actual state of the art in GPU vector graphics, which is stuff like Scaleform.)