Am I the only one who's going to point out that Fat Man and Little Boy were primitive atom bombs and totally different than any multi-stage nuclear weapon deployed today?
First though, this poll is idiotic (and I'm not just referring to the misspelling of
deterrent, even though it's annoying me). Fission-based weaponry was in development long before the decision to use it on Japan, and the research was in place well before the Second World War even began. The war accelerated the process by virtue of the Manhattan project (and the simultaneous studies going on in the USSR and Germany), but fission-based weaponry was inevitable, and the development of modern thermonuclear weapons was a logical next step. The technology itself is neither good nor bad; it just is. The uses to which it have been put have a moral component, but considering the massive leaps in technological development the nuclear arms race of the Cold War catalyzed, I would argue it's had nothing but a positive influence.
Second, the use of the primitive atomic devices on Japan has arguably been the reason they have not been used on a population since - frankly, the results were so horrific that every leader since has been unwilling to bear the cost (especially considering the development of the MAD doctrine in the Cold War).
Third, Japan was warned - twice - about the imminent deployment of both weapons and given the option to surrender. The leadership refused. The estimated cost in Allied lives to invade Japan was 1 million+ soldiers. This does not take into account the casualties that would have resulted had the Russians also invaded, a plan for which was in the works. Think of what happened in Germany post-1945 and consider the effect if the same had occurred in Japan. It's very well and noble to think that the mass bombing of civilians is never justified, but the fact of the matter is that World War 2 was the largest total war before or since and it's conclusion was the priority on all sides - all options are on the table. Those of us who have never lived through a state of total war find it difficult to grasp the concept, but the entire economy and society of the largest nations on Earth was dedicated to nothing but the war effort. That's an enormous psychological shift from the world we live in today; one that most people can't make without a serious understanding of the historical context (something high school history fails to teach entirely).
Lastly, nobody knew what the effects of prolonged exposure to nuclear radiation were. Even the Manhattan project scientists who worked with it (there's an interesting story about how they nearly caused a fission reaction in the middle of New York) had little idea of what kind of power they were actually working with. When Truman ordered the deployment, nobody knew what a long impact it would have on Japan.
The atrocities committed by Japan (and they were many, brutal, and unforgivable) don't even factor into the equation. With the information at hand in 1945, the use of the atom bombs was fully justified and necessary - and it has probably saved countless more lives since. Imagine the carnage if a modern thermonuclear weapon was ever deployed on a civilian population.
That said, nuclear technology was inevitable. The war simply accelerated it by a decade at absolute most.
As an aside, reading some of the responses in this thread makes me think that the quality of history instruction is severely lacking in a lot of places. There are some very odd, simplistic, and in some cases downright looney interpretations of actual events and "what-ifs" going on here. Anyone who thinks we live under constant threat of global nuclear annihilation hasn't looked honestly at the geopolitical state of the world in the last 10 years. We're at the lowest likelihood of nuclear war since the Soviets tested their first device in 1949.
You want to have a discussion about the place of nuclear technology in 20th century history, then by all means I'm game (I don't think Battuta has called me a 'threadwinner' in several months now, I'm losing my touch

). Facile one-line poll questions that don't even begin to capture the complexities involved are pointless.
Oh yeah, and while I'm at it, Iraq was never accused of having nuclear weapons, it was accused of having "weapons of mass destruction." This includes all CBRNE threats (chemical, biological, radioactive, nuclear, environmental), though Iraq was known to have previously deployed chemical weapons. Not saying the WMD possession accusation was justification for invasion, just that nuclear weapons were not a necessary component of the purported WMD hunt. Iraq and Afghanistan are also very small-scale conflicts compared to the general history of modern warfare. The number of troops currently in Iraq and Afghanistan combined don't even come close to the number of troops stationed in West Germany immediately following the cessation of hostilities in WW2, nevermind the actual numbers of combat troops involved in the invasion of Germany itself. 22 million civilians died in the Soviet Union alone between 1941 and 1945, as opposed to 100,000 (maybe) in Iraq from 2003 to 2010. Much as the loss of any life is tragic, the fact of the matter is that Iraq and Afghanistan are minor conflict in terms of strictly numbers, and totally irrelevant to any discussion concerning nuclear weaponry.