I've been meaning to link to this article by Mark Kleiman for a while. It's a thoughtful article about the thinking of some economists on happiness, and ties in nicely with both of the politician's lectures I've been to recently.
When asked "why is GDP so important", Brash gave the answer that it improves human wellbeing and (more importantly) gives us choices, but the underlying reason is that it in some sense makes us happier and makes us more able to satisfy our preferences. And underlying Fitsimons' talk on GDP is the idea that wealth is merely a means to an end, not an end in itself. The common end shared by both is happiness.
Three of the major predictors of happiness mentioned by Kleiman are secure employment (knowing where your next meal is coming from), wealth (more is generally better, but having more than your neighbours is better still) and lesiure time (which unlike wealth, is valued absolutely). Focusing on per-capita GDP at best only addresses one of these three factors, and (if the overseas experience is anything to go by) increases it at the expense of the other two (working harder in less secure, casualised jobs).
Focusing directly on happiness, rather than GDP growth, would suggest policies such as a shorter work week (as in France) and discouraging casualisation of the workforce.