This looks like a resurfacing of a trend I learned about in general chemistry. Apparently some years ago busineseswere trying to sell this kind of stuff on two claims: one, that nitrogen filled tired deflate at a slower rate, and two, that in an accident, a punctured tire filled with nitrogen is safer somehow than normal air (something to do with fires). What I learned in chemistry is that both of these claims are bogus. Total marketing bullshit preying on the ignorance of the usual consumer. Now it appears these same people have reared their heads again, using different claims. Some facts first of all. Air is already about 78% nitrogen and 20% oxygen by volume (
http://en.wikipedia.org/wiki/Air). Thus the company is offering what looks like a replacement of most of the oxygen molecules with nitrogen. At 2% oxygen content you have ten times less oxygen per volume than normal air.
Now to address these new claims. First, they cite facts about the bad things that happen if you don't keep your tires inflated properly. All of the benefits of proper tire inflation can be achieved with normal air. Secondly, if my education serves me well, the claim that "With PurigeN98, tires hold their pressure longer." is incorrect due to the law of effusion of gases. In fact, as rate of effusion is inversely proportional to the mass of the gas molecule (lighter molecules escape faster than heavier ones), and that nitrogen is lighter than oxygen, the tire may deflate even faster with PurigeN98 than when compared to normal air. This is of course assuming that any channels through which the gases may escape is large enough to permit either nitrogen or oxygen.
Thirdly, and I'll concede this point partially, they claim your tires will oxidize slower if you use their product. Now obviously we are talking about the oxidation of the interior of the tire surface, as the exterior is still in contact with normal air. This is were my knowledge halts my opinion. I have not taken any chemistry courses that would cover the oxidatin of rubbers. It is true that such a thing happens, as we all know, old rubber gets hard. I am assuming this is due to the oxidation of the polymer in some way. This obviously could contribute to the degredation of your tires. But, as one who tends to keep his tires properly inflated, I must say from firsthand experience that properly inflated tires will become dangerously threadbare before they fall apart from internal or external oxidation.
In conclusion, find a gas station who has free compressed air, keep your tires properly inflated, and don't waste money on this hype.
(sorry this was so long, but I hate seeing companies pull this kind of stuff on the unsuspecting consumer)