The jittery and less than stellar motion you are seeing is due to some of your source material is at 29.97. If you have footage that was shot 23.98 with a pulldown, adding that 29.97 footage to a 23.98 will remove frames every second you would normally want.
Hopefully that explains it. In other words, stick to 29.97 if you have anything with that frame rate. It will look the same on a dvd but without the stuttery video.
I would invest in Cinematize for ripping clips off of dvds. It's really simple to use and converts directly to prores at proper framrates. It even makes files with the correct aspect ratio automatically.
I found this here:
http://help.apple.com/finalcutpro/mac/10.0.4/
