This is now deprecated.
I no longer recommend feedburner if you are using WordPress or another blog platform that has a feed built-in. I also no longer recommend automatically posting to any site, including facebook and twitter. You are better off on any of the social networks, including Twitter, to tailor the message to your audience, not just use the title like most automation software does. If you want to use the power of social media, you are better off hand-crafting your messages. Sure, it takes a little time but, in the end you will give your readers a better experience. The best thing to do is to think of your readers, not the search engines. By creating a personal user experience, you will get more real readers. You will also get better search engine love. Automating content is dead. Your readers really do know the difference, and so do the search engines.
One of the problems, especially when posting to Twitter, is that your post is usually fairly long. Twitter is designed for short messages and you really need to create the best message you can that summarizes your post. You also need to make sure you are using a short URL that you can track.