Well, I had my 73727 ISF calibrated a few days ago, by Seth Schnaible of Santa Cruz, CA. Seth is one of the ones who wrote the book on dlp calibration, one of the real pro's in the field. He is very experienced with Samsung and also Mitsubishi (and probably others, too; he took the video of the NASA launch in the intro to DVE!)
It's really probably not NECESSARY to have ISF calibration with these sets; you can get a very good picture (as I'm sure most of you already know) with the amateur tools at our disposal (DVE, AVIA, etc.) But it was worth it to me to get the best possible PQ out of this set. The most important things, I think, are 1) getting the gray scale set 'right on', and 2) getting the Chromaticity Coordinates (for the primary R, G, B colors) properly set. These were both quite far off; no amount of User Menu adjustments will be able to fully compensate for not having points (1) and (2) set correctly using professional equipment.
Seth's calibration brought the Choromacity Coordinates right near the theoretically optimal values, and after this the 'Temperature Tracking' was very near the ideal 6500 Kelvin (within 100K) over the whole IRE range; beforehand it had been ~ 5800 K. Color tracking was also adjusted to be correct (100% +/- a few %) over the whole IRE range; beforehand , Blue had been ~ 90% (relative to Green) and Red ~ 110%.
So I'm very happy to have done this; the PQ is definitely more satisfactory. Is it necessary? Probably not; as many of you know, you can get very good results on your own. But if you are obsessive about getting the best PQ possible, then you should consider it.