Check out this <a href="http://www.extremetech.com/print_article/0,1583,a=121163,00.asp">Extream tech review</a> of codecs. they test a few different codecs (DivX, WMV, MPEG4, QuickTime 6.5) and then compair encoding time, quality (at 2 different bit rates, 500k and 1mb) and show pics of the different clips. interesting.