Joel Spolsky - Hitting the High Notes:

"Style. Happiness. Emotional appeal. These are what make the huge hits, in software products, in movies, and in consumer electronics. And if you don't get this stuff right you may solve the problem but your product doesn't become the #1 hit that makes everybody in the company rich [...].

It's not just a matter of "10 times more productive." It's that the "average productive" developer never hits the high notes that make great software."