It depends what you are trying to accomplish with it.
Does it yield reliable information? No.
Does it ever give anything other than desperate fictions from the tortured? Yes
Historian Alfred McCoy explains how torture used on the individual is unreliable, yet perpetrated upon thousands it can supply a small amount of real information. (In my work with torture victims, I certainly have personal knowledge of individuals who have broken under torture and revealed information or given up names to their captors.) But the latter technique is very expensive, especially from a moral/political point of view. It turns the population against you, and degrades the country that uses it. The use of torture always blows back into the society that uses it.
Torture is effective -- short-term only -- in terrorizing a society, as a form of mass societal terror and repression. This is why the U.S. uses it... make no mistake. But long-term... as pointed out just above, it turns the victims and their families against you. You can, as in Algeria, win the battle of Algiers, so to speak, and still lose the entire war and be driven out of the country, as happened to the French.
I don't like the "torture is ineffective" argument, personally. I find it is a utilitarian argument, not a moral argument. The truth is more nuanced than a simple yes or no, so susceptible to the passions of the moment (as after 9/11). Would torture be okay if it did reliably produce good intelligence? This is really the internal logic of the "ticking bomb" scenario writ large.
Would we allow cannibalism if we found it could help feed the poor and hungry around the world? We could just allow cannibalism upon the very old and the terminally ill. Why is this unacceptable to us?
Would slavery be tolerable if it produced an efficient economic system? (The latter was truly argued for some time in U.S. historical circles. See this link.)
If we argue the merits of torture upon utilitarian lines, we end up in endless debates while those being tortured continue to suffer an unending hell, while the powerful parties of the imperial land contend over whether or not their suffering is palatable enough for them.
We must end torture now. Not because it doesn't work, and not because it may, someday, backfire upon the society that conducts it. Torture must end because in the collective consciousness of humanity it is seen as evil, as destructive of common human bonds, a universal anti-moralism that eats into the very core of spirit and soul, and antithetical to the communalistic ethos of men and women striving together to survive in the world.
It must become part of a categorical imperative beyond the vicissitudes of socioeconomic or national struggle. It is anathema. It is like murder, the murder of mankind.