Except that, as someone has already said, this would end up listing all top-level packages - i.e. the ones you actually use - because nothing depends on them. This gives you still quite a hefty job for manually going through this list. It's probably just easier going through the list in YaST and trying to uninstall something - if YaST doesn't warn you, you're OK deleting it (provided the description shows it doesn't do anything important!). Try to step through 200 packages manually in YaST and remember the dependencies. And if you have found one package that no other depends on you have to start over again since the dependencies have changed.
Also, for clarity, can anyone confirm that the 8.1 version of YaST handles this automatically if you use it to do all uninstallations? That is, there should never be orphan packages if YaST is used to uninstall? I'm still not sure whether someone has found orphan packages after using YaST or not. Just try it out: Install gnucash with Yast. Yast will automatically install packages like gal, guile, oaf, slib, Guppi, gtkhtml, python, umb-scheme,.. Then uninstall gnucash and you will find gal, guile, oaf, ... still in you system. And one day you wonder why your drive is full.
Fabian