Ask HN: Sales Letters

At the recommendation of a fellow HN reader, I've been reading the book "The Ultimate Sales Letter" by Dan Kennedy.

In short, the book is a good guide on writing the sales letters most often seen in direct mail, but now frequently seen on some landing pages as well, particularly for products such as ebooks.

Based on other comments people have made here, I have no doubt that letters written like this -- long, 4-6 pages, written in a folksy, kitschy way -- are effective for many target customers out there.

My question is as follows: has anyone used this format for something besides a kitschy mass consumer product? In other words, does such a writing style work for more sophisticated buyers, such as execs or tech savvy people? The book suggests sending such letters to executives but I cannot imagine responding well to such a letter were I to receive it at my office.

What are your experiences with sales letters? Who does it work well for, and who doesn't it work well for? What changes have you made to the basic method to increase efficacy?