The webpage at http://flink.incubator.apache.org/ provides no information on why Flink is useful.
The problem is that after skimming the main page people cannot figure out why they should try Flink. I gave the link above to my friend from industry, and in 5 minutes he asked me if Flink was an enterprise Java framework.
I suggest adding 2-3 paragraphs under the "Project Overview" heading. They should explain in plain English what dataflow systems are, which tasks they solve and what differentiates Flink from its competitors.
A link to the recent VLDB paper might help as well.
PS I would like to emphasize the word "plain" in the previous paragraph.