720p vs 1080i debate
I find this explanation quite good:
Motion is different issue. If you want to see motion clearly, then live action 720p is what looks best, compared to 1080i. Here’s why: the information content of 720p is about the same as 1080i, though what it lacks in spatial resolution, it makes up for in temporal resolution (because the picture is at 1/60th of a second, not 1/30th x 2.) On 1080i, this would show as flickered or jagged edges on bright horizontal objects (like in the background of a camera pan.)
I have watched some hi-def clips on my pc (with lcd flat panel), and although 1080i has a better resolution, it is interlaced. I find if you are into action/sports type video, 720p actually performs better since there is no interlacing effects. Interlacing has always been a problem on today's progressive displays.