Creates a landing page for your feed subscription and out of the box working newsletter subscription form.
We use exactly the same technique as Feedburner - if you come in using a RSS reader, http://your-site.com/feed gives you the feed content, but if you come in via a web browser, you get a page with the subscription options (newsletter, feed links).
Since we check the HTTP referrer, we can't cache what gets served on the /feed URL. So in WP Super Cache, you have to exclude feeds from caching, see the installation guide. Hyper Cache has feed caching turned off by default and it also scores better in our tests.