I have never tried Intuition liners, but my alpine boots have Thermoflex liners and my AT boots have Thermo Inners in them. I can't imagine skiing in a boot without them. They are comforable (after they pack out slightly), exceptionally warm, light weight, and easy to pull out of your boots for drying (prevents smell).
My boots aren't 100% comfortable, but more so than any boot I've ever had without them. Thermo-conformable liners are one of the greatest advancements in ski gear in the last 10 or 15 years, right up there with shaped skis.
Having a glovelike boot fit does wonders to increase your control over your skis, so a conformable liner is an issue of performance as well as comfort. I you can afford them, buy them.