I know that this post is quite a old (a few weeks at least) but I figured I would chime in. Why? Because copy writing is one of a marketers most important skills. So it is important to get it right.
Anyways, yesterday on my TV show I covered your question with my audience. Check out the recording here at BetterNetworker (http://www.betternetworker.com/videos/view/marketing/missing-link-premier-episode
I hope it helps answer your question. Leave me a comment under the recording to let me know if it helped and any other thoughts that you might have.
And if you have the chance, you can catch me live tonight 4PM PST or 7PM EST at http://www.michaelnovak.me/live