I was really skeptical that it would justify the price, but I think it's one of the best purchases I've made. They really do hold in the cold way better. That may not seem like a big deal, after all you can buy a lot of ice for the extra $3-400. But you'd be surprised how handy that is. Your stuff gets less soggy. You can go on extended trips without having to make ice runs. For shorter trips, less ice required leaves more room for fish, groceries, etc.
A couple recent examples: I drove 14 hours from Wyoming with coolers filled with frozen/butchered antelope - the Yeti meat was still frozen solid when I got home. The other coolers had started to melt, leaking blood on the packaging. I spent the fourth of July in Yakima in 90 degree heat - one bag of ice kept the kids' milk cold for four days outside in the Yeti.
