At http://www.handtransplant.com (clever name), they have a few articles. Apparently the ethical concern is because of the risks involved with the immuno-suppressants. They feel the risks are warranted only when the patient will die without the transplant.
There was also a mention of whether doctors would "'market' themselves and make money". They didn't go into that further but perhaps they feel some doctors would not fully inform a potential patient of the risks.
I question the ethics of telling someone they can't have a procedure done because someone else doesn't like it :-)