I find the max sensitivity setting just right on the road. It doesn't work to adjust it in the driveway since the wipers are purposely slowed down when the car's not moving. It doesn't rain much in Charlotte but I always keep the wiper switch in the first (intermittent) position and just push the button to activate.

Re wiper noise, try this. Take a good window cleaner (or alcohol) and clean the windshield well. Also, wet a rag with it and wipe down the blades well. This gets rid of the gunk and build-up and quiets them. I think dealers wax the whole car when new including the windshield
You can get longer life out of the wipers doing this.

Re no rain (or snow) in Phoenix, just go to Flagstaff. I was there March many years ago. It was 80 in Phoenix but snowed in Flagstaff. On the return to Phoenix, I drove through a hard rain in the desert. They said that was a once a year event.

 

my new blades turned up today, so easy to fit, and the difference is AMAZING...silent wipers...ah the bliss (even almost makes the auto rain sensor worth using)!

 

Funny you should say that. I have driven many many cars with rain sensors (and unfortunately in Holland it's raining very often) and there aren't many rain sensors that really work well. The best I've had was in a 1998 Xantia typeII (same PSA rain sensor as the Peugeot 406), one of the first "normal" cars with a rain sensor (expensive option at that time). That one worked really very well, with only 1 exception: Too sensitive when there was heavy fog. After that car, the rain sensors got worse and worse (probably cost reductions). Most cars I've driven after that had rain sensors which were too sensitive.

The E60's rain sensor is relatively good, but there's room for improvement. I like the sensitivity adjustment, but the range should be bigger. I find it too sensitive most of the time, even with the most sensitive setting.

Note: Keep in mind that the quality of the blades affect the functionality of the rain sensor, as the system depends on good quality wipers for zeroing the signal.

 

A good point.