I would love to see this with nitinol wire muscles.

Power use would be immense and it would be insanely slow.

Power use might be high depending on configuration, but speed shouldn't be that slow using capacitors. Sufficiently strong pneumatics tend to require quite a bit of power too.

Considering 90%+ of the input energy goes to heat with NiTi actuators, Your walking robot would also double as a great space heater.