In 2005, Parker Hannifin interviewed some nitrogen filled tire users and put together a video testimonial. Note the benefits that these users have seen, and how truly impressive they are. While this video focused on commercial truck users, it is important to note that ordinary, everyday drivers should see similar results. Commercial trucks are steadfast about tire maintenance, and more attentive than the average driver. They are seeing these benefits even though their tires were maintained regularly with air.
And remember, the user that states he saw a 0.1 mpg improvement is discussing trucks that typically get around 5.5 mpg (a 2% improvement).
You can view the video here: Nitrogen Tire Inflation Testimonial Video