Hi
There was a problem back in NX9 where the Part Default Unit was not being read (PR 7101209). The final response stated that the problem was fixed in NX9.0.2 and NX10. "Unit information from the original SolidWorks file cannot be determined when converting into an NX part file. The measurement units specified in 'Customer Default -> Gateway -> General -> Part Default Units' should be used when a conversion is done."
I just tested NX9.0.3 and NX11.0.1 and found that having set the above Part Default Units that I can control the unit that is used when importing sldprt files.
Regards, Ben