I tried walking on models at the store (this was a decade ago). The biggest thing was trying to find a “simple” one as they get complicated fast. I ended up with a free one from a friend and used like 2 of the 99 “features” it had.
Someone mentioned incline, and that was good for increasing the workout factor. Mostly I wanted a way to walk inside when it was crazy hot outside.
Now I just pace the length of my living room. 😬