In addition to those he outlined, additional criteria rise to the level of "important" in my mind (and Prince never said his list was exhaustive, of course), including:
showcasing the strengths of high-level play, where PCs need disintegration to take down a wall of force, need to erase that symbol, and need to research and learn the truename of the demon to be banished (perhaps by any means necessary)
non-nerfing environmental challenges: high-level modules should not be just the usual trip to the dungeon, cave, or ruin, but should offer distinctive challenges. Examples: aerial/aquatic/undersea environs, active volcanoes, magical/spatial anomalies, demi-planes, and other planes of existence. And while physical challenges are common, social and cultural obstacles can be equally effective: urban, high-society/courtly, guild/organization based, and religious cultures and faction relationships may not only limit standard combat actions but may also shift the field of combat to influence and politics, and the repercussions of choices made and opportunities lost, rather than simple swordplay
knowledge (and perhaps even mastery) of the game system: knowing your PCs and the capabilities of their abilities, spells, and magic (both your own PC and the others in the party), knowing the foes/monsters, knowing the environment and setting, etc.
acting well as a group/team: this follows on from knowledge above, but gets into coordinated and effective application of expertise, individually and as a group, at the table and in the moment, as well as looking tactically ahead to medium and long-term goals
What other design principles guide your designs and play in high-level adventures?