The short answer, Rat: Neither 1080P OR 780P is supported by my 65" Mits!
There were(at the first of the year)rumors of 1080p in the future; my set has 1080i, but had no support for 780p at the time I bought the set in Feb.(at the time the TV was purchased I pretty much stopped researching for fear of what I might learn, and end up with "buyers remorse"! Although, Mitsubishi does send out periodic software updates, so that these formats may be supportable at a later date, since my understanding was that there were no hardware issues, such as scan rates, which is pretty close to the limit at 1080p, involved.
I was given the impression, back then at the first of the year-and I may be way off base here, but I was given the "impression" that 720p was more for gaming, and other "non-TV"(computer hook-up, etc)inputs. That cable has the ability to use 720p, but due to bandwidth concerns probably won't. That HD DVD may use 720p(but can be up-converted in the TV to 1080i)with no discernable change in PQ, so...720p was, to me anyway, "at the time", a Red Herring. I was also given the impression, again "at that time" that the average person wouldn't be able to "See" the difference between 1080i and 1080p anyway, I dunno....
We made the decision that seemed best "at that time". I have no doubt that if I were to start researching again today, I may well come up with a different result in the "next" four or five months. The industry just won't hold still long enough!
The fact still remains that the TV has a fabulous picture, lots of comprehensive inputs, mature technology, exceptional reliability, has no bulbs to burn out, is somewhat upgradable, is emenently affordable, weighs a whopping 330lbs and takes up almost as much space as a King Sized bed!
We LIKE it!
Rich.