How do you mean observe tension?
Ive tried them, but i dont think they're really usefull, except for the scales.Most excersises are terribly repeatetive and boring, and because of that you tend to play them like automated wich isnt good. So you'll need alot of self-discipline to make Hanon worth the effort.
You definitely need a good amount of self-discipline to become a good pianist anyway. And anything can be played with musical expression, even garbage.
I can't imagine doing all 60 exercises in one day or all of them in an hour. Does anybody know if Hanon was a phenomenal pianist? I don't I recall reading about him in Shoenberg's "Greatest Pianists" book.