I bought my first pair of these to climb Mt Kilimanjaro 12 years ago and they kept my feet nice and warm right to the top. (The snows of notwithstanding!) My feet are always cold, so I have since used them whenever I know I will be standing out in the cold for an hour or more. They are great for winter walks, and completely essential for standing still on freezing concrete at a football match.
I would say without hesitation that they make experiences that would be memorable only for how cold my feet were memorable for whatever I was doing instead - I don't mind the cold much if my feet are warm.
If you are worried about your feet feeling uncomfortably hot, let me assure you that unless your shoes are very, very loose, your feet don't feel hot, just comfortably tepid.
Give them a try!