It solves multiple problems such as a lack of human donors and the fact that animals are appropriate research subjects because they are similar to human beans in many ways. Animals themselves benefit from the results of animal tasting animal research is highly regulated. Animal testing and Xenotransplantation is a good idea.
No, ethical consideration is not enough to discourage xenotransplantation in saving human lives, nor should it be. The saving of a human life should come before and above all other considerations, as the saving of lives is the ultimate ethic. Therefore, other ethical consideration cannot be enough to discourage xenotransplantation.
Xenotransplanation will not be trumped by ethical concerns. Unfortunately, organ failure in humans is a very real problem and many people die while waiting for organ transplants. I believe sometime in the future you will see the use of xenotranspants in an attempt to save these patients, rather than simply letting them die waiting.