Wow, thanks for the great write-up trabbic. I couldn't have installed this in my Forester without your help.
Just in case anyone is interested, I have successfully installed the Spec.B steering wheel with stereo controls functioning with my Eclipse AVN5435 HU. I needed to use a PAC SWI-ECL (ECL for Eclipes, they have a bunch of others) to act as an interface between wheel and HU. It was very easy to program the interface. Info on products can be found here: http://www.pac-audio.com/