[Animats]

The previous Spot robot was also all-electric. Hydraulic power was needed for the bigger machines. (Also, Raibert liked designing hydraulic systems; he has a patent on the valve/actuator combo used in BigDog.) Cube/square law - mass increases with the cube of the size. This is why insects have tiny leg cross sections in comparison to their length.

Battery life will be a problem, but it's clearly agile enough to plug itself in for a recharge.

[sharemywin]

you could also have some kind of stand by packs waiting.