Today I got the AATileGenerator based on cairo into a useable state. This way software-rendering is done by cairo instead of the pisces rasterizer.
The relative results are quite pleasing:
On the positive side, most benchmarks improved by a factor of 2-3x :).
However cairo is no cure-all. The ductus rasterizer used in Sun's proprietary builds is still the winner in all tests.
Most likely this is the result of cairo beeing a two-step design:
First a path is tesselated into trapezoids, and later those trapezoids are rasterized, whereas ductus rasterizes directly.
However a positive side-effect of this design is trapezoid rasterization can be parallelized, so on dual-core systems it should be possible to get close to ductus.