Stephane, I see that this one has new life, and yes, there's no reason to become bored with the subject as long as the technology involved isn't grasped firmly, and unfortunately some of the comments here have been as incorrect as the contention of the salesman that started this. There's no "native data" problem with respect to 1080i transmissions; all 2 million plus pixels are the original real ones. None of this is "discarded" when the two fields of the 1080i transmissions are combined into one full frame.
A CRT HD set is inherently interlaced in its operation and the persistance in the screen phosphors results in the two fields being automatically combined for viewing; no deinterlacing processing is necessary.
HD sets other than CRTs are inherently progressive in their scanning(i.e., the full frame is displayed in one swipe, not two), so when presented with an interlaced input it has to be first deinterlaced electronically to combine the two fields into one full frame. When properly deinterlaced the full 2 million plus original pixels are reproduced without loss and the 1080i material has greater resolution than 720p material, which has only 900K plus pixels. As Nick pointed out(probably he had Gary Merson's tests for HomeTheater Magazine in mind)not all sets properly deinterlace, and in that case a better picture results from having a player, receiver or separate video processor do the deinterlacing instead, as has been frequently pointed out here.
So, the botton line again is that 1080(i or p makes no difference in regard to resolution)resolution is superior in resolution to 720(rapid motion is a separate subject), as the several charts and graphs of resolution/screen size/viewing distance combinations illustrate.
