A few things I noticed in watching Episode IV today.
1. If the Imperial Solider had just shot the escape pod down, containing R2D2 and C-3P0, then the events of IV, V, and VI would not have occurred. Do you think the Emperor or Darth Vader ever think about that? Do you think he and his superior officer were punished for not having shot it down?
2. Luke first ignites the light saber, in Obi Wan's hut, directly at Obi Wan. A few degrees more and it would have gone straight through Obi Wan thus negating any training he could have given Luke.