Honestly, I feel that history shouldn't be tampered with, because everything we are today is as a result of actions and decisions that occurred in the past... which sounds redundant until you think about it... Would you still be the same person today if you hadn't had to live through the trials and hardships, if any, that brought you to this point in your life? This includes world events - society is shaped, both small and large, by global events as much as local.
Still, it is always interesting to see the "what-ifs" - I love reading Harry Turtledove for this reason... so I guess there you have my answer.