It is a filter - not a gas saving device.
The stock fuel filter is around $35+ and good for about 10K miles. It filters down to 10 microns.
The CAT filter used in the Nicktane system costs around $14 on ebay or at CAT dealers and filters down to 2 microns. Since it is installed before the stock filter, you should not have to change the stock one near as often. Add the that the fact that you are sending a lot fewer hard particles through the fuel, your injectors should last longer too.
Is it worth the money? Since I don't have any idea how long you plan on keeping your truck, or how clean the fuel is where you are located, I can't say.
I plan on keeping my truck at least 10 years and traveling all over the US and Canada, so I added one to my truck when I had less than 3K on it.