I too like very much the unpainted version of the Triplex. I have a small number of the "Pilot" and "Engineering" locos. I think that there was even a pilot model offered of the Lionel die-cast Baldwin Centipede. Sorry I missed that one.
So, yeah - that unpainted Triplex is my favorite of the series. I am a modeler and a basher, so I believe that is one of the reasons I like them - their visibility as models.