I've got a bunch of the cars, and they roll like greased lightning. They'll even find the low spots on your (supposedly) level trackwork.
The locomotives are fairly good runners and pullers, but some of them suffer from over-oiling and "headlight blink syndrome". The cure for this is apparently to separate the loco and tender, and apply 12vdc to the two outer pins of the loco-tender connector, which are wired straight to the motor. Let it run for an hour or so, until "all the smoke has been let out".
Yes, i'm serious. This is apparently the fix recommended by Blackstone themselves.
The new high-side gons also include the interior step-angle casting, for helping the laborers who shoveled it out empty actually escape of the interior of the car. I've never actually seen that modeled by craftsman, much less a major manufacturer.
--Drew