Its generally not the best idea to play exclusively echjebm piloted crafts while you are still learning how to play, and while observing mechjeb might teach you a few things it can easily become a crutch for inexperienced players. Though it cant really teach you precision landing, or planetary intercepts, which are very important for more challenging and ambitious missions. But most importantly, dont be one of those whiny players that needs mechjeb for everything and without it seem to find some simple things (ex. docking) almost impossible.