...to seek out new life and new civilizations

Video card drivers installed with Ubuntu 8.04.1 LiveCD are not enough to take advantage of all ASUS F3Sr video card possibilities, a 'third party' driver should be installed. Luckily there is an application that manages everything: just run System -> Administration -> Hardware Drivers: it knows there are better video drivers and asks you to install them.

After installing these drivers I could enable "Extra Visual Effects" and screen savers motion switched from jerkily to smoothly.