Yup. One of the Fun things that are less known that comes from n-body orbital mechanics is the instability of orbits. You can't just leave your satellite out there and fast-forward two years because you have an Eve mission going - your satellite needs to make correction burns as other bodies perturb its orbit.

http://en.wikipedia.org/wiki/Orbital_station-keeping

But anyway, I still hope that Principia mod (the n-body simulation addon mentioned elsewhere in this thread) will get released. This will really bring KSP into Dwarf Fortress level of enjoyment. Also, you'd get to make some really weird-ass stuff:

http://images.scholarpedia.org/w/images/f/f6/NbodyChoreoGamm...

http://tuvalu.santafe.edu/~moore/crisscross123.loop.gif