Well, there is a massive increase in response when using Fly By Wire systems, but an increased workload on the entire mechanism. Fighters are given specific pre-flight checks, specially with regard to wire transmission etc (older planes had the wires running along the outside of the fuselage for just this purpose). Commercial airlines tend to avoid it due to maintenance costs, but it's entirely possible that the performance flexibility of FBW would be an advantage as long as the airlines are prepared to maintain.
Backup systems on Commercial aircraft are staggering. Practically everything in a Boeing 747, for example, has about 3 auto-kick backups, and planes from 180 passengers plus these days have auto-landing systems which means that both the pilot and the co-pilot could be out of action, and the plane could still land, be it on a runway, in the ocean etc (though has been pointed out, you don't land a 747 in the ocean, you crash in it)
Most Air tragedies these days come from either Structural fault, which is the responsibility of the ground crew, or traffic control error.
