I installed the rain guards yesterday after work. I received them about two weeks ago. Ordered them on a Sunday and received them on Wednesday, so +1 for speedy shipping. I didn't install them right away because the instructions said the adhesive cures best above 65 degrees. I was going to wait until the temps got in the area of 65, but I am impatient when it comes to stuff like this. Each night I swear I could hear them calling to me from the garage "Install us...Installlllll us" So yesterday I pulled the car in the garage and cranked up a space heater. Everything went pretty smooth. I will probably to an installation report with mock install photos in the next couple days. I didn't think about it until I had one side done, and at that point I didn't want to stop to go get the camera.
Anyways, I drove in this morning and couldn't notice a difference in wind noise. My commute does not involve the interstate, so I only got up to about 55 mph for a couple of miles. I'm sure there is a slight difference, but I wouldn't notice unless I could flip a switch to toggle between having them and not having them. I should mention that I have a Yakima rack with a fairing and 76" bars that stick out almost as far as the side mirrors. Most of the time, including right now, I have a Thule box on the car as well. I can't even tell the difference when I take the box off or put it on anymore. When I bought my first OB, a '99, I didn't have the fairing. The first time I drove it on the interstate I knew I needed a fairing because of the howl from the rack was awful. I can't imagine the rain guards making that big of a difference.
I'll have to wait for it to rain to see how they do at keeping water out with the windows cracked. I'll give updates when I can.