With the cost of diesel fuel still well above $4/gallon, commercial and municipal truck fleets can really benefit from nitrogen tire inflation. Clemson University (in conjunction with Michelin and Ingersoll Rand) released an over the road study in 2008 that showed truck tire life improved by 50% with nitrogen filled tires. Fuel economy also improved, approximately 3%. This corroborated a lot of the findings of a 2007 Canadian study on filling tires with nitrogen. Drexan Corporation, using a large test fleet and over 1M road miles, determined a 3.3% improvement in fuel efficiency and a 50%+ increase in tire life. The results of that test, which were presented at the Clemson Tire Conference in 2007, can be found here:
Here are some thoughts from truck fleets that are currently using nitrogen tire inflation, and you will see that they each measured significant benefits.