Just how well has the 'nudge unit' done?

Broadcast at BBC News:Nudging – concept of changing people’s behaviour without recourse to the law but to psychology – has been one of the big policy ideas of the last few years
The coalition government set up a “nudge unit”, officially called the Behavioural Insights Team, in 2010. But just how successful has it been?
David Halpern, who heads the unit, told the Today programme’s Evan Davis that it has enjoyed a wide range of successes. He said that by adding the line “‘most people pay their tax on time’ to a letter you get a significant increase in the number of people who pay their tax on time and you get a reduction in complaints.
“It turns out it’s a nicer way, to encourage people than to threaten them.”
But Professor Gerd Gigerenzer, director of the Max Planck Institute for Human Development, told the programme that he did not “object against nudging per se but against the philosophy underlying it, namely that basically that people are born more or less stupid.”
There is, he said, a real alternative to nudging, that of educating people to become “risk-savvy citizens: to invest in to making people competent”.