Awesome! Looks super similar to an old sideproject of mine, www.bookshrink.com. The algorithm's different -- yours is aimed more towards summaries, while mine was aimed at sentence importance.
yeah, I'm working on adding more summarizer algorithms. I've been thinking on the lines of weighing up rhetorical questions, weighing down exclamation mark (cheap sarcasm detection) etc.
I experimented with giving bonuses to proper nouns and verbs, as well as giving a slight advantage to shorter sentences.