Here’s my test of audio/video screen capture using Silverback, in which I use Google to find Waldo. It was recorded on a Mac OS X 10.5 machine with a Logitech Desktop Microphone.
The final Quicktime video is 468×300 pixels (about 25% of the original screen size) It is 1.01 minutes long, and 19.22 MB in size. The original video was full-screen, and far larger in size: about 120 mb, but there are export settings that can reduce that size considerably.
Observations: Silverback was very easy to configure and use. I assume the large file sizes are because it’s capturing both the on-screen video and video of the user, coupled with a high screen resolution my Mac. It records as Quicktime, which PowerPress was able to play back in Firefox and Internet Explorer without any problems.