The sales letter format should emphasize key points while maintaining simplicity. Do not repel the customers or clients. Have normal spacing between lines and the contents just right so that the reader does not feel over_burdened reading your letter. Get the reader to feel as if he is invaluable to you and your company. The pronoun "you" in place of "we" instills a sense of warmth in the reader, drawing them closer to your business.
You do not have to worry much about being a copycat if you do not find the most unique cover letter format in town. Just be sure that the contents of the letter have a clear and definite direction. This will bring about a good flow in the contents of the letter.