Thank you.
I, too, needed something like this forever. Every time I see a long article, I complain about the lack of a tl;dr.
Unfortunately, I am not so optimistic about humans creating the content. You guys have a really, really hard job. Creating the right tools is easy. Convincing people to create tl;dr's is hard.
I'm really curious about how you are planning to solve this problem.
I really do hope that you'll succeed though : ]
Edit: Also, for me, this tool is great for articles that are new. Assuming you don't have enough contributors at the moment, after seeing a few articles that don't have tl;dr, I probably use the tool less and less everyday. Until I forget about it. I'm sure I am not the only one.