The one I saw was doing it on a flat stretch of sand, and I’m sure the narrator said it can travel at twice a human’s walking speed. Not that I’d be walking if I saw one of them rolling up behind me. 
The umbilical system mentioned in today’s version of the column (I don’t remember it being there before) was discussed in full, with diagrams, patent references, etc… It apparently is possible to provide an umbilical that doesn’t get tangled up.
**John W. Kennedy ** said:
It was. Well, I remember it.
puppygod said:
Not necessarily. All it takes is 1 wheel. But you need to be able to balance. But if a two-legged animal can walk upright, balance is not an obstacle.
Bumped.
This Wiki article is now on the front page there: Rotating locomotion in living systems - Wikipedia
Interesting that Wikipedia doesn’t mention the umbilical possibility for connecting a wheel. If someone had a source for it it could be added.
Powers &8^]
Shows a diagram of now something could have things connected such that rotating continually in one direction will unravel itself by design after two revolutions. It’s probably too difficult to evolve though.
The biggest disadvantage to having wheels is that they have no dual function. You can use feet to attack someone / kick their head in / slice them with your nails. How would a predator be able to grab onto / slice something open with the wheels after it runs its pray over? How would a herbivore it be able to kick / fight back with no feet?
How would an animal be able to make tight turns on chases with wheels? (rubber wheels need to be replaced often due to loss of mass on turns and breaking)