When I open and watch a capture from Screenium's Media Library, the mouse pointer jumps around so I can't really see what I'm doing

This problem should be solved with the release of Screenium 1.4. Where it occurs, it's both a playback problem and a recording problem. Mac OS X 10.6 comes with the new QuickTime Player X which in spite of its new technology and advancements in other fields doesn't play our videos as well as the former QuickTime Player 7. We recommend you download it for free and install it in addition to the QuickTime Player X.

Download QuickTime Player 7

On the recording side, Screenium 1.4 vastly improves the mouse rendering speed to be on par with the Desktop recording perfromance.