I don't have much experience on my own, because I only tried camtasia once. It seems to work fine, at least for a short video.

Recordmydesktop(http://en.wikipedia.org/wiki/Recordmydesktop) is recommanded by an artist, David Revoy, who made quite long videos on his Linux system for a DVD called "Chaos & Evolution". But there was some converting necessary, because the resulting ogv-Format couldn't be edited smoothly with MEncoder (http://en.wikipedia.org/wiki/MEncoder)
Then he edited the videos in kdenlive (http://www.kdenlive.org/).