I know its an old thread, BUT...I just bought a NP Challenger and it's GREAT!!
I've repaired some of these for folks, mostly cherry switch problems, and have had a chance to run these some. They are well built, very good running engines...I figured "why not?"
I'm normally a Lionel, O gauge, TMCC/Legacy guy but I do have a loop of S-54" in the middle of the layout and like the few TMCC Mikados/Pacifics I have. I'm really impressed with the Challenger and have enjoyed operating it for the last few days. Glad I took the plunge after all this time...there is something intangible about running new American Flyer under TMCC/Legacy that is just plain COOL.
Joe
~Long Live Lionel~