Evaporative cooling kits for cars? vs aircon??

[Logic]

I know that in DRY AREAS (non humid) evaporative cooling works extremely well as long as you feed it dry air and exhaust the humid/cooled air.

ie; They DONT work like aircons where you shut the cool air in. You have to open windows etc appropriately.

So while looking at the science numbers again I had the bright idea to Google:
evap evaporative cooling kit for car
Surprisingly a LOT of hits came up. (that I have not yet looked at)

So I was wondering if anyone has experience with a car evap cooler?
Economy gains vs aircon? (You do have the added weight of having to carry water around)
Reliability of these kits?

[oil pan 4]

Evaporative cooling works great till it doesn't.

[Piotrsko]

It is one of freebeards often posted pictures: a VW with one hanging off the side window of an aircooled VW.

They work when the relative humidity can allow the incomming air to evaporate quickly (hence the name) and in a desert can drop the air 20 degrees. Don't work well in Chicago or many places East of the Mississippi

[freebeard]

The only time I tried one, only the door windows rolled down, no pop-outs. I confirm that doesn't work.

[cRiPpLe_rOoStEr]

Roof-mounted evaporative coolers are widely used in trucks in Brazil.