[pixelmonkey]

"In the evaluation in section 7 of the paper, Heron beats Storm in every single metric."

In every metric except perhaps the most important one for actual users:

Storm is open source, Heron isn't.

Also, the @TwitterOSS account indicated that there are "no plans to open source in the short-term":

https://twitter.com/TwitterOSS/status/605460461761396736

[frankmcsherry]

The paper contains the motivation: "For our needs at Twitter, we needed a stream processing platform that was open-source, high-performance, scalable, and was compatible with the current Storm API."

I guess 3/4 isn't bad.