Why would you buy it again? Because it's cool to say that you have it?Got mine 2 weeks ago from infiniti dealer for 425$. They had 2 in stock at the time. Possibly was the only 2 left in the nation until ams next batch.
Do I feel it made a difference? Not really. I did replace my old super dirty stock filters with brand new ones 5 days before installing for a more accurate comparison.
Do I regret it? Not at all.
Would I buy it again? Of course.