Data Sift has a similar product, they aggregate everything.. I think this is more keyword driven and you can choose what you want to. More power to the user.
You're able to whip up your own feeds. Main difference is how its visualized/presented to the user and I don't think they do sentiment.
*side-note: For Butterworth, I think one of the questions we'll have to address is. Just because the sentiment is giving us a value, how is that reliable sentiment because it is just 140 characters. (I think Manuel told us a statistic about this but I dont recall)