Does the "Energy Catalyzer" by Andrea Rossi et al. generate energy by converting Nickel to Copper? From Wikipedia:

The Energy Catalyzer is an apparatus built by [...] Andrea Rossi, [and] Sergio Focardi. The 2009 patent application claims "a method and apparatus for carrying out nickel and hydrogen exothermal reactions," with production of copper. Although the patent cites previous works on cold fusion, one statement by Rossi asserted that it is not cold fusion, but rather LENR, Low-Energy Nuclear Reaction.
[...]
According to Focardi, "the hydrogen is heated at a given temperature with a simple resistor. When the ignition temperature is reached, the energy production process starts: the hydrogen atoms penetrate into the nickel and transform it into copper.”

Are these claims true?
 A: The energy catalyzer probably does not work. Here is an entry point to some of the criticism: http://tech.groups.yahoo.com/group/H-Ni_Fusion/message/226.
The criticism that nuclear reaction can't take place at low temperature is no good, because  Palladium/deuterium does it. Rossi is saying that, like Palladium, Nickel allows for nuclear reactions, except that he has the Nickel/protons fuse together to produce copper instead of the deuterium with deuterium. Fusion of protons with Nickel is an exothermic nuclear reaction (unlike what the previous answers claim), but it is prevented by MeV scale electrostatic barriers, not KeV scale barriers, and is energetically as far from d-d fusion as d-d fusion is from fire.
Rossi's device probably doesn't work, but without a completely sound theory of cold fusion, one cannot be 100% sure. The major problem with the demonstrations that Rossi ran is that the measurements of heat output are done by assuming that all the water that comes into the system is converted to steam, and this is a very unreliable way to measure heat output. You should just use water to measure heat, that's what everyone else does.
Rossi claimed that all the steam coming out of his machine was dry. But dry steam has a huge gas volume, and should rush out in an invisible jet of gas out of his pipe, while his device emitted a "feeble mist" (to quote the linked page). To make mist, all you need to do is to charge water up electrically, so that it breaks into droplets, and that doesn't take any energy at all. The device could be producing no energy beyond the electricity going into it.
Rossi claimed to make copper, and he submitted a sample of Nickel powder with copper and iron inside that he said was the product of his machine. But the copper and iron were analyzed by others and have natural isotope ratios, which is extremely unlikely for the products of a nuclear reaction. The reports of Nickel/Hydrogen cold fusion, unlike Palladium deuterium cold fusion, all come from essentially one place, with no independent reproduction. It is possible that Nickel hydrogen doesn't do anything at all.
But there is no reason to dismiss Rossi a-priori. He claims his device works, and this can be tested by just waiting to see it work.
EDIT: Here is a related answer on the difference between steam and mist； Difference between Steam and Fog / Mist
Here is an update reflecting more recent news: Is the E-cat by Andrea Rossi et al. for real?
A: I suppose I did not make myself clear, and spent too much time talking about stellar evolution.
The main reason why this cannot work is that, when you are working with elements that have atomic numbers higher than Iron (26), you cannot get energy by converting an element into another that has an even higher atomic number. In this case we're converting Ni (element 28) into Cu (29). That conversion does not generate energy, it uses energy. Fusion only generates energy for atomic numbers below Iron; above it you can only generate energy through fission. This is why I mentioned stars: they cannot "burn" to any element above Iron. It needs energy from the gravitational collapse of a supernova to create the higher elements.
This is because Iron has the highest binding energy of any nucleus, as explained here and here. Adding more protons or neutrons to Iron means you have to supply energy. Below Iron it's the reverse. This is why fission bombs use Uranium (92) or Plutonium (94) and fusion bombs use Hydrogen (1).
A: The transformation of Ni into Cu would require extreme temperatures. In nature, stars can convert elements into other ones. During the normal burning phase of the star, it converts Hydrogen into Helium. This happens at about 10 million degrees (C or K). When the Hydrogen is used up, the star contracts further, heats up more and gradually creates the other elements up to element 26 (Iron). The temperature is well above 1 billion degrees (1GK) when this happens. That is the end of the star's energy cycle as creating heavier elements requires energy instead of releasing it. 
Heavier elements such as Nickel (28) and Copper (29) are created when heavy stars collapse on themselves after they reach iron and can no longer balance the gravitational pressure with the generated energy. That explosion is called a supernova and is visible across the universe.
As you can guess, you're not going to reach a temperature of 1GK with a heating element, and even that would only get you to Iron. The reaction to convert Ni into Cu will never generate energy: you need to add (lots of) energy to make it happen. Even cold fusion (which requires a measly 10 million degrees) turned out to be a false alarm. So I'm sorry, this kind of energy generation is completely impossible. This product is quite clearly a con.
For more information, try Wikipedia:
Evolution of a star
Nuclear binding energy
This graph shows how Iron has the highest binding energy. In other words fusion (from light elements) up to Iron, or fission (from heavy elements such as Uranium) down to Iron will generate energy. However, fusion from Iron to heavier elements requires extra energy.
