Ian talked about his aspirations for compiling assembly shaders (e.g. GL_ARB_vertex_program) to GLSL IR back at XDC2011 Chicago.
As said on Ian's blog, "This project has turned into such an incredible rat's nest of irritation that I can't even believe it."
The good news is that he's now hit a big milestone by running Doom 3 binaries with the assembly shaders in GLSL IR. However, there's still issues like incorrect rendering and needing to disable HiZ. He has posted some screenshots from Doom 3 showing the progress on Intel Sandy Bridge.