I'm happy with my Ziebart. Just point out where you don't want them to spray. I didn't know about the wheel wells at the time, so I didn't ask them not to spray them. My skid plate wasn't sprayed, but I guess my guy just listens better than Phil's
You can also opt to go in for a yearly checkup/touchup on Ziebart for 34.95 or something.
Pretty cheap for a big "peace of mind."
Also, it may even dampen some of the underbody sound as that is part of the treatment. So less sound on the interior for all!