I hope someone in the know answers your question. I would like to add some, on topic:
Having chosen OpenGL, should one choose:
1. Texture from Pixmap, Shared Memory or Fallback? 2. Nearest, Bilinear or Trilinear? 3. Direct Rendering? 4. VSync?
So, as to my experiences regarding your question...
I use Intel graphics. In Fedora 9 alpha, it was not possible to use OpenGL, only XRender, which supports less effects and is slower, I thought. Since Fedora 9 beta and the actual Fedora 9 release, it is possible to use OpenGL, which I now use without any apparent problem. I have set options: Texture from Pixmap, Bilinear, Direct Rendering and VSync, but haven't a clue which are best, but I assumed that turning them all on would give me the fullest user experience. It would be nice to know which is the best choice. I am very pleased with the effects and performance.