I believe copy makes or breaks a sale, but I also believe site aesthetics (design, IA, imagery etc) make or break a sale. It’s very frustrating to see that sites that fulfill criteria 1 fail in criteria 2 and vise versa.
Case in point:
Bonsaiboy.com: Unknown site with great copy and ugly design
Redenvelope.com: A very well known site with superb aesthetics and worthless copy