i wanted to share my initial opinions on the DFI feature since i assume that some peeps might be interested. the DFI demo mode runs in a split screen and allows you to see side by side the difference between dfi on and off. for the most part, the differences are so subtle that you'll end up spending too much time looking for the better setting. currently, i've got DFI on and i'll probably leave it there until i really spend some time calibrating the tv. when i do go to calibrate the set, i'll start with the DFI turned off because i think the positive aspects of DFI can be achieved through adjustments in the user menus. if you have, or plan to purchase a 732, you can probably pretty closely emulate the results of the DFI with adjustments to your various color, brightness and contrast settings.
now, my background is in graphic design in print media, so i'm approaching this from that perspective. what the DFI seems to be doing is very similar to the process of adjusting image levels in photoshop. Basically the shadows are being darkened, the highlights are being brightened, and the midtones... well, you got me. they are either being held constant, or there is some center value where all shades above that value are brightened and all shades below that value are darkened. anyway, this is how it appears to me.
and it is subtle... because it has to be. the problem is, i don't know if it is subtle enough. the DFI is throwing in one more little push of contrast, but it seems to be doing it not only between dark and light, but between the shadows and the midtones and the midtones and the highlights. my experience, again not directly related to video, is that by doing this, you run a much higher risk of banding issues and losing that nice smooth gradient from lights to darks. although i have not seen any banding problems, there were times yesterday that i felt the DFI was pushing the highlights a little too hard and i thought i was losing some detail in the lighter midtones.
anyway, don't know if this helps, but that's what my experience was with it. i'm going to leave it on for now because it does add depth to the OTB settings, but i'll be turning it off in the near future.