tseg - I love your thoughtful assessment of what to look for in a vacuum. It reminds me of when Steve Jobs was looking for a new washer for his family (talked about in his biography). He dwelled over options for months, and made his family weigh options in discussions at the dinner table. After an extremely thorough analysis of a product he initially knew little about, he imported a Miele front-loader (when front-loaders barely-existed in the US), and he said it brought him immense joy whenever he used it.
I will echo other enthusiasts, in that an air-powered nozzle generally can't replicate the power of a motor-driven brushroll (except maybe a Turbocat with a truckload of suction behind it). Many air-powered nozzles can do a very good job at surface cleaning carpeting, but they're limited to the amount of suction driving the brushroll; this usually means they have softer brushes that may surface clean well (and offer the illusion of a great clean), but will leave behind the dirt and grit embedded in carpets and rugs. No amount of positive reviews from average users can hide this dirty fact.