We've got a VW Polo Bluemotion in the car park at the moment. I drove home and back, across London in heavy traffic, and it averaged around 45mpg. I was a little disappointed, I guess, as my old long-term S-Max used to average about 40mpg on the same trip.
As soon as I got onto the open road, however, the eco-gap opened up and the Bluemotion was doing 55-60mpg, which is much closer to the claimed figures.
The biggest shock was its ride. When I drove our German test car a couple of months ago I was surprised at how rigid the ride was on its admittedly high-pressure, low-resistance tyres. Well, they must have been over-inflated, because this car has an excellent ride, yet the VW press office has confirmed it is mechanically identical to the earlier car.