Under-rated - liner/compression socks. I typically use them religiously and they are not really noticed, a pain to put on, but otherwise easily ignored or forgotten about. But any time I actually do forget them I spend the trip bleeding, blistered and sore and spend every step thinking about those damn socks sitting at home in a drawer.

Over-rated - craft beer. There are too many of these things in the liquor store now. Most times I go into a liquor store and don't recognize the vast majority of the selection. I don't know how many times I've gotten back to the van, ready to enjoy a tasty beer after a hard hike and it turns out the craft beer I thought I'd try for the first time is some hipsters impression of what a beer should taste like. But really its just bad beer disguised as craft.