I remember watching a similar program. After a long and interesting history of the Ejection seats, it then went into detail about the problems of a supersonic ejection.
The conclusion was that an attempted ejection at 800mph using a traditional ejection seat would be suicide - the pressures involved would kill you. I remember seeing a picture of a test pilot who "bailed out" at I think supersonic (or just below) - his face was unrecognisable - black and blue with completly bloodshot eyeballs that were twice there normal size. He was lucky to survive.
The solution was to seperate the whole cockpit, not just the seat, from the rest of the plane in one sealed unit. This meant the pilot was not exposed to the force of the external air pressure.
In real life however even with that system, the chances of survival are slim.