RAMESH PONNURU'S NATIONAL REVIEW ARTICLE, WHICH PRESTON LINKS TO, IS ALSO EXCELLENT
Glenn Reynolds is fond of saying that the anti-cloning position boils down to anti-cloners finding cloning "icky", or aesthetically revolting. Then pro-embyonic researchers proceed to make the case for theraputic cloning or embryonic research based on aesthetic properties -- the blastocyst is only a microscopic cluster of cells, it hasn't formed organs, etc.
The truth is the "anti-" anything movent is always based on aesthetic revulsion. It doesn't matter what you pick -- terrorism, racism, slavery, sexism, etc., if you ask "why" long enough you'll eventually get to "it's just plain wrong!"