I think of undercoating as sound deadener and rust guard. I live in the rustbelt. 13 years ago I had it done to my Honda Prelude. It was a great investment back then. Honda had great reliabllity, but their sheetmetal would rust out too quickly after only a couple years. My Prelude never rusted.
Now, with the what they do at the factory, "supposedly" aftermarket undercoating and rustproofing is a waste of money...apparently may also void your factory rust warranty if not done properly. (Not sure why they try to sell it to you at the dealer though).
I want to keep this Pilot for several years, at least, and was thinking about doing the same thing. If it starts rusting from the inside-out shortly after the warranty lapses I will be upset. Research it bit further though. Let us know what you decide and why.
Living in Hawaii now I thought of the rust proofing or undercoating as a necessity. The salt air off the ocean and the red clay, not like Alabama Red Clay, volcanic red powder dirt, and sand wreaks havoc on automobiles over here. It gives me peace of mind and if anything goes wrong I can place the blame on someone and have a fix for it. It's up to you if you think you need it ... for the most part I would say no ... but being the most expensive car I've bought to date, I figure I would protect my investment.
A friend just picked up his new Harley six months ago, because of the salt air the chrome is already starting to pit and some parts rust ... Don't know if that attests to Harley quality or actually the salt air ...
I'm wondering how much sound deadening is offered by the undercoating. I would consider paying a few bucks for a quieter ride. Would new tires or undercoating make more of a difference for the money spent?