I am thinking about upgrading my 720P Sanyo PLC-Z3 to a 1080P projector. In my search I found these diagrams dealing with viewing distance vs. resolution.
Don't know if you've seen them before, but thought they might be interesting!
My viewing distance is 11.5 feet and I have a 78" screen, that's close to full benefit of 1080p.
http://www.carltonbale.com/ has some good articles about the subject
