Would've started off with a non shadow casting bulb object with a mental ray area light(not set to visible or emit specular) inside and a light surface shader on the filament object. Plug a nice temperature controller shader like a blackbody or mib_cie in the area light and light surface color. Set the light surface to contribute to reflection and fg, turn on "use lights", connect light's translate position to eval point, and drop the light into the "lights[0]" slot so I can control the light surface's brightness with my light's intensity instead of having to tweak both. Then crank out an incandescence pass to use in post to control the glow. Bah, done rambling now.