I know that when the bomb was dropped, my grandfather was on an island in the Pacific, staging for the invasion of Japan. All the men knew that their chance of survival was very slim. They were told to expect over a million casualties.
I know that the bomb being dropped instantly changed Japan's priorities, and likely saved my grandfather's life. Many, many lives were spared by our using the bomb. (particularly, American lives) Was it pretty? No, but it beats the alternative.
My grandfather had squared off against the Japanese on both Guadalcanal and Peleliu (where he lost his foot and a portion of his leg), so I can understand your take on that particular situation.
My contention, and I'll admit it's wholly academic, is that another way could have been found. The only restraints in the path of those potential-other-ways was the imagination and ingenuity of American commanders, the political situations (foreign and domestic) at the time, and the desire to see the "boys come home" as quickly as possible.
In a scientific sense, Hiroshima was unneccessary, in my opinion, and the decision was driven not by military factors (i.e. efficiency and avoidance of casualities,although the bombs certainly helped in these ways) but by political ones. And that even when the decision was made, the aftermath with regards to Japan, was certainly far different that what had been previosuly stated as Allied war aims.