I'm not sure where some of the Atlas hate is coming from earlier in the thread. I have two SD35s from the first run in 2000 with TMCC and RailSounds. I upgraded the motor drivers with a CC-M and they run as smooth as butter now. None of the early locos that lacked Cruise/Odyssey ran very well at low speeds in comparison to modern locos. This isn't because of the drive train, but rather the electronics.
The SD35s I have are extremely detailed and not any harder to work on than MTH or Lionel locos. The additional fine detail makes them a tad fragile but that sort of thing is to be expected.