I don't believe this is true (I own one). I believe the firmware in the device has been modified and those modifications can be taken advantage of when using Spectraview II. According to NEC they are not accessible to 3rd parties.
This is an interesting piece of information. Here in Europe, Nec doesn't even sell colorimeters but integrates a calibration matrix stored in the profiling software, just like Eizo for example. I had always been under the impression that the USA approach with spectraview was different... may be rather than custom filters they simply store the calibration matrix in the colorimeter... still, I wouldn't discount the custom filters approach I mentioned. Are you sure about just the firmware being different in your Nec i1?
Also, regarding the filters made out of plastic in colorimeters, I know that to be true for the i1D2 but I thought that the DTP94 had glass filters...
you are also right regarding the different results that one could get with several "identical" colorimeters, the interinstrumental agreement doesn't seem to be their strongest point. However spectrometers loose their calibration too and that's why the i1pro should be sent to the factory for calibration every now and then.
hoffsta, I use a windows machine.
Manny