Over the years, I've heard arguments both ways on Ziebart services. Personally, I've had great luck with their products. I have taken each of my new trucks over the last 15 years directly to Ziebart after purchase to have their rust protection package done on them. That package includes the body undercoat, frame and suspension undercoat, and drilling and spraying all of the body panels. I had my 2010 crew done earlier this spring for $400 out the door. I also bring them back for the annual inspection/respray which runs $35 at my local Ziebart dealership. So far, I have not had one speck of rust on the vehicles I've had done there and they look like brand new underneath. Knowing the salt and other stuff that is used on the roads around here, it's rather amazing.
There are other companies out there offering similar services that I'm sure are also very good. But, I have only ever used Ziebart and consider it money well spent.