I read a review somewhere that the Wigo fails in city driving because the fuel economy drops to a level comparable to 1.5L MT engines. I believe the reason stated was that the engine isn't VVTI, which means the combustion isn't at its best performance.
The Wigo is still the best kei kar around. However, if you're getting the top of the line Wigo, you might as well get a Mitsubishi Mirage. The looks aren't as good, but for the same size and performance, you get more features.