I like about 3 screen heights for DVD watching. For cable TV stations, depending on the quality of the station, I usually zoom it down to 4+ screen heights because the lack of resolution is noticeable. If I had satelite or digital cable, I'd probably zoom it back up.
I sit 15' away from a 13' wide screen. Or 2X screen height.
The picture is a bit soft for NTSC sources, but 90% of my viewing is movies, and DVDs scaled with a HTPC to 1365 X 1024p, and HD scaled to the same resolution look excellent at that distance/size to me.
[This message has been edited by Dean McManis (edited 11-08-2000).]