Well I did, and thats why im writing this post.
Firstly, not all cats are effected by cat nip. Scientists say around 65-80% of cats react to cat nip and that the trait is inherited.
To be completely honest, its awesome. I can watch cat videos for hours of cats tripping out on cat nip.
The reason behind this strange behaviour is that cat nip has an oil in the plant called Nepetalactone. This oil is absorbed through the nasal tissue of the cat and binds to protein receptors that stimulate sensory neurons. When a cat is effected by cat nip the "high" only lasts a few minutes and then the cat will acclimate to the cat nip and become unaffected. Most cats require a few hours away from the cat equivalent of devils lettuce before they will be effected again.
Cat nip has little to no effect on older and younger cats, so you will only know around 7 months if your cat can become an addict.
Scientists Don't know exactly what nepetalactone does to the cats brain, and why their behaviour becomes so strange, but least we get a show and i'm sure they cats love it.
Below is a video of a bunch of cats on cat nip, I'd suggest indulging in this video as it is a bunch of cats, on cat nip - What more do you need?
Sources:
http://www.petmd.com/blogs/thedailyvet/jcoates/2011/june/cats_and_catnip-does_it_really_get_them_high_and_why-11271
https://www.scientificamerican.com/article/experts-how-does-catnip-work-on-cats/
https://en.wikipedia.org/wiki/Nepetalactone
http://animals.howstuffworks.com/pets/question303.htm