First, the engine does not need to run for the vehicle's a/c to work. It is totally electric, just like the brakes and power steering. I have been sitting in the car, say at a stop light, and the a/c is blowing cold and the gas engine has shut down. This was of huge importance for me since I live in Phoenix where it can get into the 120s in the summer. Since I just bought my Highlander LTD Hybrid I haven't had a chance to see how well it works in the high heat, but so far it works great. I like the auto function, all you do is adjust the temp you want and it takes care of the fan speed and location.
I did buy it used with about 14k miles on it, so I got it for a good price. I bought it from a lady that leased it in FL and she lost about 10k on it because of the buy out of the lease. We looked at a new base model with the AF package #1 for about 33000 before sales tax and dealer add-ons using our Costco auto buying program, but spent less than that and got a loaded LTD with DVD Nav. -Good Luck!!!