I have used mine on both my projector on a 127 X 54 screen and on my Pioneer Kuro Elite FD-151 (60") plasma. It works on both and improves the image on both (depending on personal preferences and settings, of course) - but, it is definitely more noticeable on the Projector/Screen than the plasma. The Kuro image is definitely enhanced, but it is far more subtle than the large projector/screen (Epson 6010/Stewart 137"D 2.35 aspect) at the same Darbee settings. I enjoy both and, in fact, am ordering a 2nd unit from AVS so that I don't have to keep switching the unit between the two displays. Bottom line, IMO, if you have a real HT with projector/screen you will likely appreciate the enhancement more than on a plasma. But that's not to suggest you won't like the plasma improvement - just that it's a bit more subtle if the image is already tweaked well, as my Kuro is.
"You cannot reason a person out of a position he did not reason himself into in the first place." -Jonathan Swift