They have been using Nitrogen to fill tires in racing for the last 5 or so years. It is being marketed by several tire discounters as a better way to inflate then the traditional compressed air. While most people don't know the difference, they do recognize that they use Nitrogen in NASCAR, so it makes for a very good promotional item. They have something to Bragg about to their neighbors or co-workers.
The benefits of using Nitrogen in the racing world is for consistency. Compressed air has alot of moisture in it, when H2O or water is heated it expands, cooled it contracts. That very function is what Nitrogen counter acts. Nitrogen by nature has an affinity for water, the phone companies and fiber optic people use it every day to keep moisture out of their lines, so they can keep a clear and clean signal. in racing, they use Nitrogen in the tires so they say at the pressures they want. Put moist air in a tire and as it heats up, the pressure increases. Now this is nothing new, you heat a gas and it will expand, only by using Nitrogen they know exactly how much that expansion will be. The compressed air is ever changing, and so is it's moisture content, hence you have a rate of expansion that is not known.
In the everyday world, I don't think it matters if I have air or Nitrogen in my truck tires, but in the competitive world of racing, yes they have to use it.
Nitrogen is used in racing shocks to pressurize the oil. Raise the pressure and you raise the boiling point. Since it is moisture free, it also allows the oil to remain moisture free. As most know, water and oil do not mix or so the saying goes. What it Will do Thu is cause the oil to foam, and since oil can not be compressed and foam can be. Foam in your shocks will change the way the shock perform, just like if you were to change the valving.