Mine works phenomenally well - especially as an afterthought with the house not being designed around it - but the climate is different enough between Phoenix and Prescott to matter.
There has never been a high-temp/low humidity day that this $400 window unit didn't keep temps under 75 inside, and I've seen 103 outside here. It's in an otherwise unused room on the lower level (north side) of the house, so it's rarely seen or heard. Now, when monsoon season comes along and outside humidity gets above 30%, efficiency is essentially nil - it just makes it clammy inside. Having a respectable AC unit is still a requirement for a brief part of the year here.
I wish I could design a house with evaporative cooling in mind, there are lots of little things that would make it more efficient. Plumb it into the central air system and install up-ducts that vent into the attic - send the relatively cool, moist house air into the attic and flush some of that heat load as well. Put several solar panels on the south side of the house or on the roof to shade surfaces while generating the power to run the cooler.