KSP is great in the way, how its attract peoples to the theme of space exploration. Their designers wisely pick up some fantastic space system, to attract people to the real problems of the space exploration.
Well, it may be seemed that KSP is a rival of orbiter , but its not, in any reasonable meanings. Orbiter is much closer to our solar system. KSP gives basics of orbital maneuvering in very obvious way (and Orbital not intended to do so). Orbiter requires a lots of skills to desin a mod craft, and KSP requires much less of them, serving as introduction in modding and engineering.
KSP still needs some carefully designed campaign mode, that will provide learning curve and historical oversightof space exploration. But that is easy to believe, that authors would mnged that task with grace. And if not - Hey !- There is hundreds of modders to help them.