I'm going to compare this game to real life for a second. Even though this is just a game, I try to play it like I am a real Astronaut. In real life Astronauts DO use a lot of computers to "fly their ships". However, in-case of a computer malfunction, real Astronauts MUST be able to do everything on their own. So my opinion on MechJeb is this. If I can do a maneuver perfectly on a repeated basis, then it is fine to automate it. If I can't do a maneuver perfectly on a repeated basis, then I need to keep practicing until I can. I have no problems with using MechJeb if I can do it myself first.