Zalmans are pretty good, but there are better coolers for the price. At one time they were one of the best. They have a few new models but havent changed/improved there older models any. What are you putting it on?
For dual cores they are decent, however one issue with it is for the price there are far more coolers out there that are better. Some better options are the Xigmatek S1283 for the cheaper areas, and for higher end the IFX-14, TRUE, Megahalems, Venomous-X, Noctua NH-D14/NH-U12P are all better options for the price.