The only Orbiter users who need to know anything about orbital mechanics are add-on developers, especially those who make navigational MFDs. That's all WAY over my head, so salute to them.
However, regular schmucks like me only need to know enough to use these add-ons. And most of what we have to know is the sequence of button pushes on the MFDs, and maybe which 1 or 2 numbers to watch in each stage to know when to push the autoburn button. We need no more than the most basic sketch view of the actual orbital mechanics involved.
I must disagree. To reach ISS you need orbital mechanics.
The concepts in this tutorial [ame="http://www.orbithangar.com/searchid.php?ID=3074"]Tutorial: DG to ISS[/ame] are orbital mechanics.
Interplanetary travel is not only pushing a button and let a burn to take place. See this tutorial [ame="http://www.orbithangar.com/searchid.php?ID=3403"]Tutorial: Concepts for Interplanetary MFD 4.2.1[/ame]
Physics has 2 sides. One is to understand the math and the other is to understand the problem. Math is performed by MFDs, but you still have the problem.
So orbiter makes us to become familiar with concepts we were not used to. We still need to solve problems. The level and complexity of problems you want to solve rely on you. Orbiter is the tool for that.
This is why Orbiter has been good for my workshops for primary school kids I had in 2006, and it is also a delight for aeronautic engineers, NASA and ESA personnel who also play Orbiter. So it is simple and complex at the same time, unlike Super Mario.
As for rocket scientists, one thing is to design a rocket, and a different one is to fly it.
With Orbiter the boundary between user and developer is hazy. When you edit a scenario you are stepping into the realm of developers, and you can make simple or complex mods.
In my case I made Mesh Wizard. Was I a wizard for making it? No. 3D rotation matrix was already invented. So making the tool was more a matter of persistence and method than mathematical genius. Even if Mesh Wizard is intensive in geometry and math, code is in charge of handling it. I only had to turn my understanding of a problem into code, not into math.
So those are the reasons why I disagree a little bit.

