one of the main default export settings out of Motion i use is "Lossless + Alpha Movie", and it is defaulted to non field render, so i made a new setting that is field rendered. i've rendered out the same project both ways and see no noticeable difference. am i crazy or shouldn't a field rendered movie look a lot smoother (at least where images are moving) than a non field-rendered??
Field render= interlaced. You would notice the difference much more on a TV. Personally I see no reason to ever use interlace render unless you're integrating interlaced footage for an interlaced finish. Even then, interlaced animation can look iffy.