Funnily enough I was interviewing one of the head Pentagon boffins over the phone yesterday- a sort of droning autist- and he said they're working on a robotic centaur armed with machineguns! Do they just watch Terminator all day to drum up ideas?
That thing would never make it over some of the terrain that dog thing goes over. Watch the video. the guy actually kicks the thing sideways and it sticks out its leg to keep from falling over, and he really gives it a good shove.
The drawback is that it's really, really, f*k'n loud. I saw this thing a while ago in a youtube video, don't know if the one on the site posted has sound.