I recently started listening to Seth Godin's podcast, Akimbo. If you're interested in marketing or just a new way of seeing the world, I highly recommend it. I also started reading one of his recent books — This is Marketing. In doing so, I've found a new a way to describe the crux of what product design is all about.
Like most great ideas, it is so simple.
Make things better, by making better things.
I love it. Makes me look forward to going to work each day.