Getting tired is a feature. It's a health positive design for a past time that has traditionally been sedentary and contributory towards a health epidemic.
Also experiences designed with this sort of locomotion in mind will take into account the energy expenditure - because it becomes obvious once you start using it. To that end, things like faster modes of transportation become more meaningful and useful for the player, as does the sense of distance and scale (imagine walking a kilometer out of town and having to walk back to do anything useful). None fitness and space oriented experiences can combine it with movement methods like teleportation for user convenience.
Depends on how you use it. If you use it as per the video (sticking it in your pants), it's a bit limited.
If you use it by holding it, it essentially turns into a pointer that allows you to easily decouple motion of direction from your torso and head (and thus allows you to strafe or walk backwards as needed - point it behind you to walk backwards... although the implementation is a little flawed because it doesn't change the speed of motion (we don't expect to travel backwards as fast as we do forwards).
