I like the Atlas/roco car well enough. Unfortunately after putting a bunch of the more detailed, newer Intermountain cars on the layout, the older cars with cast on detail do not come off as well. But in a train, you can't tell. I like the Atlas/Roco car better than the WEaver PS1. I just like Riveted cars better and the weaver car is a model of a welded side car.
The Atlas Master 1937 boxcar body is from the Intermountain dies I think. I understand that Atlas bought all the O Gauge tooling from Intermountain which included the 1937 ARA Boxcar, a Steel Reefer, one of the tank cars, the USRA Gon, and USRA hopper. Atlas replaced the underframes or reworked them to use their trucks.
I have built a number of the IM kits and I find that the fragile detail parts in styrene do not stand up well to operating sessions compared to similar metal parts. Most of these have been rreplaced with metal on the Atlas cars. They would make good kits. I don't think I would get too excited about the train man cars as kits or builtup. Their detail does not match the other stuff.