Hi Keith - it seems like Carrara may have regressed in import functionality from previous versions, I don't remember having problems with I think it was Carrara 7.

I don't see anything that you'd set on that import options, but I did find this discussion thread here with someone else discussing a similar problem:
http://www.daz3d.com/forums/viewthread/48202/

The part of particular interest is:
"looks like theres also a on off switch “smooth” which turns of the auto smoothing and uses the the original obj data"

So try going to the "surfaces" pane and try flipping the "smooth" switch to the opposite value - it seems that by default it ignores the imported normals (which are the ones you want to be used for the shading), and instead calculates its own ones by averaging polygon face normals, that is what will lead to shading artifacts. Hopefully with that behavior turned off and the original normals being used you will see those artifacts go away.

Also in that thread is is mentioned: "Normals aren’t stored in Daz studio either, they rely entirely on the smoothing angle." - if that's true then I'm afraid that means DAZ studio just won't work properly for rendering CAD data since it is unable to use the vertex normals that are stored in the file.

Hopefully that surface option will fix it for you - it seems unfortunate that this used to work more easily in Carrara and seems to have become problematic in recent versions.

- Michael