If you're particularly overweight or have joint/back or other health issues you may want to consult your physician about how to improve past a slower paced walk. But if your joints and heart are otherwise healthy, it's pretty good exercise for getting in better shape, losing/maintaining weight, and for getting to spend some time outside in the sun and fresh air.
Depends on how fit you are, I guess.
I need to train at higher intensity to "feel" it as excercise.
nonetheless, it's a great way for people to start, if it's not a solution for the lazy, like "hey I walked thirty minutes home from work, now I deserve my sofa"
