Compiling and installing Nvidia binary driver solved the problem with DVI and made the screensaver run smoothly.
I already had a first-hand experience with one of the drawbacks of a monolithic kernel: even minor patches may break kernel modules which were compiled and installed separately from the kernel itself. After I downloaded and installed an updated kernel, all of a sudden there was no sound (I had installed the latest version of ALSA) and an OpenGL screensaver was crashing Gnome. Could have been worse. Recompiling and reinstalling both the Nvidia driver and ALSA module resolved the problems, but it has to be done every time I install a new kernel version through Update Manager. I’m still considering my options.
External hard drives is another headache – drive manipulation can only be done by root, but after creating and formatting a partition regular users have read-only permissions on it, and I cannot find a way to fix that without firing up the terminal window.
These are minor details – I can deal with them, but for an average Windows administrator could be a show-stopper as in “Where’s the checkbox??!” BTW, Linux adoption is picking up – check this out.