Mhhh, good work, they are getting there, but it won't be the real thing until the hydraulic pump comes on-board.

"In its current version, Cheetah is powered by an off-board hydraulic pump" - well, I can understand off-board power supply because batteries are not that good yet and THE REST of technology of robotics should continue developing because batteries WILL become better, but what's the point of developing something which can not function without most essential of its part being somewhere close connected with pipes?

Interesting, but it looks like the black n yellow beam that is attached is giving it stability. If it could achieve this speed balancing itself, I would be properly impressed.
More so, if it could do it with it's own power supply, even if only for a short burst of time.

Interesting, but too unstable looking to be very practical in my opinion. Quadruped is not at all ideal, but just what we are used to. Any decent attempt with robotics should have at least 6 legs, and maybe 8.

Cool, but I'll be a whole lot MORE impressed when its propulsion system is entirely on-board. Granted, the tether does look slack, so it's probably not stabilizing the gizmo.

Some part falls off at 0.13 / 0.14. Imagine what would happen in rough terrain. Can it make corrections based on terrain and moving targets at that speed like animals and humans can?

Exit foot, to the left, at about 0:14.
The first thing I notice is that the left and right feet are operating in sync with each other. No animal actually runs this way. Springboks and similar animals use all four legs together in hops. But generally, animals use each leg separately. Well, not really seperately -- in sequence. The way I like to imagine it is to imagine a wheel. The wheel has four spokes, all on the same side of the wheel, equally spaced for the basic configuration. I think that should be the goal.
Also, add wrists and ankles. There need not be power to flex these joints. They can function in a springlike fashion. Use something like Oscar Pistorius used in the Olympics.

The cheetah perhaps shouldn't be designed to run faster than the average human, since someone is going to need to run alongside it holding the tether, power supply, hydraulic pump equipment, while someone else will need to run alongside it to hold the controller arm. It's a nice experiment, but still has a long way to go.

Ah, Laura, then I guess you haven't heard about the CSV (Cheetah Support Vehicle) being developed for just that purpose. It's the size of a tank, contains a massive power generator, and supports the Cheetah with a large boom. Goes 30 mph, so no worries.

Arachnid model would be more effective.