Intensity as the be-all and end-all of working out? Absolutely not!
I think working out smart and maintaining fitness in a healthy way (and having fun while doing it!) are what is important. A balance of intensities is the best way to go, and we each have to find the balance that works for us.
Also, something that seems intense to one person may not seem so to another. For example, the same workout of one type will seem less intense to someone who is used to that type of workout (step, kickboxing, spinning) and more intense to someone whose body has been training in that type of workout.
High intensity cardio? I'm really not feeling the love for high impact (and neither do my knees or hips) so I limit it and modify (trying to find challenging substitutions for moves that are still high intensity, but not so jolting).
I do think that there is a distinction to be made between 'intensity' and 'impact.' Some seem to think that high intensity = high impact (and maybe for them, it has to be?)
I think at times, impact can be more than is needed for a certain level of intensity. As a personal example: my cardio of choice in the late spring through late fall is outdoor speed walking. I can truck along at close to a 5 mph average for 3-5 miles or so, including some small hills, sweat like a pig, and get in a very intense workout, BUT rarely do I feel it later in my knees or hips (unless I try to do too much too soon). On the other hand, I can do one high-impact/high-intensity workout with no modifications and I can feel it the next day.
Another example: I've done Cardio Coach workouts (interval workouts on CD that you can use with equipment) on my rebounder, which reduces the impact, but allows for high-intensity sprints (at least they feel high-intensity to me, YMMV!)
I find that higher intensity weight workouts/rotations make me hungrier and more tired and, for me, the results may be nice, but they are not maintainable at that level. Something a bit less intense is both more maintainable and doesn't spike my hunger as much or make me as tired.
I have done 'every day" challenges in which all of us worked out to some degree every day. For that, I definitely varied intensities and workout modalities, doing one interval workout per week (I might get away with 2 in a not-every-day rotation), heavy upper-body weights one day, heavy lower body another, and a circuit workout on another day, with kickboxing on another day, and one day for stretching/yoga and another day of moderate cardio or core work (depending on what I felt I needed).
That offered me a doable level and amount of intensity for me.