If this question were moved to the Science Discussion Forum, you would be able to collect viewpoints from all aspects of the philosophical spectrum, I'm sure. You have posed one of the most highly loaded questions faced by medical science now and in the years to come.
"Ethics" can be defined as "the discipline dealing with what is good and bad and with moral duty and obligation." Ethical issues, therefore, are addressing whether or not a particular practice is morally acceptable and useful for humanity.
Cloning could, at some point in the future, offer beneficial options for treatment of conditions such as heart defects or Parkinson's Disease. This could be called therapeutic or nonreproductive cloning and could be considered an ethically acceptable use of the procedure.
Cloning could also be used for reproductive duplication of the entire genome of one being, potentially leading to an identical copy of the original. This use of cloning raises serious ethical questions. Research into uses of cloning may require the use of embryonic cells and there are objections to the destruction of embryos in order to obtain these cells.
There's going to be lots of debate and few definitive answers for many years to come in response to your question.