Really cool API, you should port this to concord! =)
i'd say major diff is dynamic topology. So during the pipeline execution you can add/remove workers for any stage.
Also each stage/operator can be written in any programming language.
Storm/Flink/SparkStreaming/etc... all have much higher level API's. We built the execution engine first, these great things (DSL, etc) should come soon. For example this API would be easy to support to execute on top (the pipe abstraction that is)
Here is an example of a DSL we prototyped in a couple hours.