My answer would be no, but not because I would be worried about paradoxes or radically changing the history which has led us to this place, as such. WWII has had quite a deleterious effect on our world, and if there were a way to retroactively prevent it, I think it should be prevented.
The problem is that Hitler was the product of a particular "wave" (for lack of a better term) in history. He was not an extraordinary man, so much as a man who was in the right (if you can call it that) place and time. If he were to be killed, there would have been another fuhrer, and the holocaust, WWII, and all the appurtenant horrors, would still have ensued. Indeed, it was Hitler's own megalomania that made it possible to defeat Germany in the first place. Had he not insisted on personal control of the panzergruppen leading up to, and on, D-Day, the AEF would have very likely been thrown back into the English Channel, and any forces coming up from Italy stopped in cisalpine Gaul.
So, as much as I would like to kill him, I would leave him alone. I think my efforts would be better spent trying to convince more people to not buy into the antisemitism and jingoism of the day. If there would have been just a few more like Dietrich Bonhoeffer, or Hans and Sophie Scholl, fewer people might have met a horrible fate.
