Recently I updated my i945GM based notebook to Fedora-15 (mesa 7.11 pre-release) and gave the java2d-OpenGL pipeline a try again.
To my surprise, it worked:
OpenGL pipeline enabled for default config on screen 0
i915_program_error: Exceeded max nr indirect texture lookups (6 out of 4)
i915_program_error: Unsupported opcode: DDX
Its still dog-slow and crashes every now and then - but it clearly shows things are improving in the open-source opengl driver world. The OpenGL pipeline seems to be a rather tough beast, as it requires lots of extension/feature and even the proprietary nvidia driver break it from time to time.