Twitterfeed is a service that allows you to link the RSS feed from your blog to automatically create Tweets. It can be a huge time saver, but it does come with a downside. Automating posts like this feels a lot like shouting to me.
Seriously, how hard is it to create 140 characters. If you are posting something to your blog, you already have a good title (cut and paste) and you can create a nice short link through Bit.ly to track the number of clicks. And that is the whole process, unless you add a couple of extra words as editorial.
When Twitterfeed made some programming changes and flooded Twitter streams with mountains of old posts, sometimes several times over, one realizes the danger of automating conversation opportunities.