The misters from Lowe's seems to cool when there is nothing else. It says on the box it can lower temps by 20 degrees, but that would be just a "feels like", not an actual change in temperature as you can see below.
You also need some breeze or the mist will soak you eventually. It's also good not to wear glasses while being misted.
On a scale of one to ten, I would give the mister a seven.
The basic package comes with 5 mist nozzles for about $25. Installation is easy, just hang and connect a garden hose.