Gallium supports shading language and as someone pointed before, it can be used to wrap Warp3D/Wazp3D functions over MESA, and hardware-accelerate all the applications using it on far more modern graphic cards.
Are you saying that Gallium has OpenCL now? As far as I can tell the GPGPU acceleration currently depends on the closed source proprietary drivers provided by the vendors (nVidia, AMD), even on Linux.
If you're just talking about shaders, well I don't find them so exciting, at least when considering the monster cards such as Fermi. If hardly makes a difference if you can render your game in 60fps versus 600fps.