I work at Wallaroo Labs.
strmpnk had good content for answers for 1 and 2. thank you for that!
re: 3.
The one stream updates/one stream reads is detailed in the "MarketSpread" example in the post. I suspect the key to your question is "two independently deployed streaming states". Could you elaborate on what you mean by that? I think if I understood that better, I could give a good answer to #3.
4. Currently all pipelines have a source and a sink. In your HTTP call example, that would most likely be a combination source/sink where we want to have both the input and some output result flow back out. That currently isn't supported in Wallaroo although we have had discussions about what that might mean. You could do transactional processing where you receive an event and then reply but at the moment, the reply would need to go out over the sink which is a different channel than the source. I'd be really interested in working with folks who could benefit from a combination source/sink approach. We prefer to add additional functionality after working through use cases with interested parties. We find that leads to better results than our designing in a vacuum.
5. Everyone has a different definition of novel. In my view, most streaming systems have left the handling of application state in the hands of the programmer. You can keep it in memory for speed but then you have to manage the resilience of that in-memory state. Wallaroo makes that in-memory state a first class citizen. It's not detailed in this post, but Wallaroo can provide resilience for you state so that if there is a failure we can bring that state back. Currently that involves using a write ahead log that is stored on the local filesystem. We are working on replicating that log to other nodes in the cluster to provide additional resilience.
If i was to hightlight one feature to answer your question about novelty, that would be it. We have a lot more content on the blog that might answer your question better. The post in question is very much a "how do I do X" sort of post rather than a "Why Wallaroo?" (of which there are a couple on the blog).