That article makes no sense. Leopard not compatible with Tiger? Of course it is. Of course it is more difficult to merge two operating systems than it is to install a new one. But of course Apple took this into thought. Maybe the people who had issues had tons of 3rd party software, hacked or edited small things in their computer, or had previous issues and thought Leopard would fix them.
I'm going to do the "Upgrade", and not an Archive and Install. My copy of Tiger is brand new.
QuickAG, when are you going to upgrade?