...throw highly intensive applications like virtual machines and animation software at my PC and expect it to handle it with speed, stay responsive, and complete tasks quickly and efficiently, and mostly have a few clock cycles spare for running something else if I want to as well.
...run 3 30" displays off my system and expect them all to run at 50 or 70fps with all 12288000 pixels of the 3 screens updating at the same time.
...run a decent number of VMs at once, say 8 or 12.
...edit impossibly large images and still have a responsive system.
...keep an insane (1000+) number of tabs open in Firefox, indefinitely.