Ah, yes, this discussion. My answer: 100% yes. Definetly. Here's my argument why:
The US had beat Japan back to its home islands and had sorrounded it. They needed to end the war. The obvious, conventional answer would be to invade it, as they had done with so many other islands. But everyone knew that would be extremely costly. The Japanese had successfully proven that on Okinawa and Iwo Jima. And those were relatively small islands with a single occupation force. What happens when the Japanese were fighting across their entire island, with their entire population?
Undoubtedly we would see everyone who usually wouldn't fight, such as young and old men, and maybe even women, fighting the American forces as happened in Germany. The Japanese were already preparing for this and instructing their citizens how to fight against an occupation force. And they would be fighting with the fanatacism of defending their home island, it would be much more vicious. Even when the main fighting was over, there would probably be guerilla forces continuing to kill Americans. Again, as we saw in Germany. So it would end in millions of people dead, not to mention that Japan as a country would have been absolutely devastated. They would be recovering for decades, and we wouldn't have been able to help them rebuild as we did. If we had invaded, Japan would be in much worse shape today.
So consider that scenario. Millions of Americans dead, many more millions Japanese dead. The entire population devastated. The entire country devastated. Probably recovering for decades. Definetly not as productive as it is today.
And compare that to what happened. Two nukes. Only a few hundred thousand people dead. Only two cities mostly destroyed. And look how quickly Japan recovered, and how successful they are today! Personally I don't see how anyone could think it was a better idea to not nuke them.
Remember that the choices were only to nuke or invade. There was simply nothing else to do, and even if you can think of something, the US military wouldn't have done it. It was those two choices, and Truman made the right one. You think the Japanese would have surrendered any other way? They didn't even surrender after the first nuke. The Japanese had purposely conducted the slow, bloody defense of Iwo Jima and Okinawa to prove to the Americans that they would never surrender. Little did they know that they were only helping the Americans to a better choice.
And don't include all the people who suffered and died from the radiation and cancer and all that after the bombing. Remember the Americans had no idea of those effects, were horrified when they saw them, and swore to never nuke anyone again. So yes it sucks, but it can't be used to argue that they shouldn't have made that decision at the time.