But performance per TDP is what matters. Battery technology is getting better much slower than CPU technology. We're already at the point where CPU speed is "good enough," but we're not at the point where battery life is "good enough."

I've downsized from a Core 2 MBP to an iPad. It has 1/4 the RAM and runs at half the clock speed. Do I care? No! Web browsing is fast and fluid, photos load plenty fast, editing documents in pages is plenty fast. And it lasts through my whole 12+ hour workday, letting me leave the charger at home and often not even bothering to charge it every night. That's huge and much more important to me, and I'd imagine most people, than whether it can be imperceptibly faster.