i'm not sure with the one that no need to wait for it to load, but actually, to get a video from youtube , we do not need any software. after a video has finished loading, simply go to temporary file[can be found in  coutrol panel>internet option>history>view files] find the ones from youtube and with a big file size. copy the file out to desktop[or whereever you want] and rename it with anything ending with .flv . done~
if you want to convert it into .avi, find a converter~

^^