Pluto or bust!
The centaur is a remarkable piece of technology, took a long time to develop, but it's the best escape stage around. LOX/LH2 engines are always nontrivial, no matter where they are used.
The Russians were the first to develop escape-stage technology, with the Block-L unit of the Molniya rocket. Lots of hard problems associated with this type of vehicle. It has to be able to start and stop engine in zero-gravity, so you must fire ullage engines first to accelerate the liquid fuel to the bottom of the tanks. And then there is the tricky problem of 3-axis stabilization and guidance. The Russians used star tracking, as well as inertial sensors. Actually I'm not sure if Centaur does this, I need to study our own rocket technology more.
The current Russian escape stage is Fregat, which has the advantage and disadvantage of using non-cryogenic fuel. This means its efficiency is less, but it can do long-term missions. For example, the Fregat stage stayed attached to the Phobos probe to Mars and was able to do both the escape from Earth parking orbit and the insertion into Martian orbit.
