I just changed mine also, using the same thought process I mentioned earlier. I used OEM parts as I had put poly's in my wagon and felt them to be quite stiff. In any case, two things;
1. I have steel control arms and the rear surface, where the rear bushing sits, was quite rusted. The front surface was clean and shiny. I was surprised as there is little rust where I am and supposedly the PO was from this area. I cleaned up both sides as best possible, but am going to get some aluminum arms at the 'mall'.
2. Even though the above was true, and the bushings I took out were not obviously degrraded, there is still a pronounced improvement in handling, quiet, and general steering control.