i can't help but love KSP. But I wish it was easier to just design the craft and missions, and not have to do the manual control. I like flight sims, but KSP controls are a bit too wonky for my tastes.
You need to get used to kOS scripting language but it is extremely powerful. You can script your whole mission from launch to landing to return. So it can be used for autonomous probes simulations or to automate parts of the mission (Apollo style).