I think I have discovered something interesting about the 7.11 fglrx driver - it accepts the options "Textured2D" and "TexturedXrender" in xorg.conf. I haven't found anything about these options anywhere, but from what I can tell, it enables the GLESX module, and presumably is supposed to accelerate 2D and the XRENDER extension.

I have a Radeon 9550SE in an AGP 4X slot. Using both "Textured2D" and "TexturedXrender", performance of the "x11perf -aa10text" test increased from around 75,000/sec to 135,000/sec.

Here is the part of Xorg.log about 2D acceleration:
(II) Loading extension GLESX
(II) fglrx(0): GLESX enableFlags = 14
(II) fglrx(0): Using XFree86 Acceleration Architecture (XAA)
	Screen to screen bit blits
	Solid filled rectangles
	Solid Horizontal and Vertical Lines
	Driver provided ScreenToScreenBitBlt replacement
	Driver provided FillSolidRects replacement
(II) fglrx(0): GLESX is enabled
(II) fglrx(0): [DRI] installation complete
(II) fglrx(0): Direct rendering enabled
(==) fglrx(0): Silken mouse enabled
(==) fglrx(0): Using hardware cursor
So, does anyone know anything about these undocumented options? I presume they're not mentioned anywhere because they're in some kind of alpha state?