I recently acquired an undecorated SD70I Canadian cab from eBay (should be pretty much the same) for $42 US - couldn't pass that up!
I haven't compared it as far as accuracy goes, but the detailing is fine and crisp, and it has a lot of add-ons to be applied - fans, grabs, wipers, sanding lines, operating ditch lights and functional nose door (unless you're a klutz with the glue!). The lights operate on a 6-diode constant lighting circuit with the actual micro bulbs poking through the shell for illumination (no lenses), 2 front and two rear, with the ditch lights being optional add-ons.
As far as running, it's only made a few trips back and forth on an 8-foot stretch of track on my modules, so it's far from being broken in. It's definitely quieter and smoother than the previous Athearns, even the recently upgraded blue box ones. Not quite as smooth as my Kato SD40-2's, but not far behind. Maybe once it gets some miles under it's belt... I don't have any Atlas loco's to compare it to, unfortunately.