Irronically enough, this is the concept behind the game Command & Conquer: Red Alert.
In the game, Einstein devoloped a time machine in the fifties, and someone went back and killed Hitler. In turn, Stalin took over Europe, resulting in the almost exact same type of thing, but with Russia and Stalin, not Germany and Hitler.
Anyways, here’s my take on the whole situation:
Now, let’s assume that if I did go back and kill Hitler, I would be able to travel back to the present time, and be in that altered time-line. Well, let’s say because of my actions, I would normally not exist, but my time machine simply put my self from the past into the present, so there I am, a man with no identity in a world I don’t know or understand. I would have no knowledge of the past 60-70 years of history. And who knows, maybe technology would be less, or possibly more, advanced. It’s a fact that war causes technology to increase faster than times of peace. Without WWII as we know it, life could be drastically different. This could easily cause me to try and fix my actions, by going back and stopping myself, let’s say. But maybe I don’t believe myself, and kill Hitler anyways, or do some other action that radically alters the future, and no matter what I do, I can never get back to the time-line that I know, because it is always containinated by my actions, however seemingly insignifigant.
Another point to keep in mind, is that millions of people died in WWII, if those millions lived, they would procreate into hundreds of millions in the generations that followed. Maybe one of those persons becomes a world leader and orders a nuclear strike at some other country? Or maybe he becomes a scientist and cures all known diseases, sounds like a good thing, but then we have a HUGE population problem. Any number of things could happen with a whole new set of people living in the world.
So no, I wouldn’t kill Hitler, the repercussions are just too unpredictable and frightening.