I've been playing around quite a bit with MapR Streams for various projects and find it to be a great technology. It has rough edges though, and one of those is for connectors that make streams more usable in the context of the CDP.
Getting data in the streams is fine, especially now with the Kafka REST Proxy, but getting data from Streams -> MapR DB and from Streams -> MapR FS is not currently built in. It's difficult for me to feel the converged as an application developer when this kind of component isn't available, built-in.
I'd also add that not having a GUI streaming solution like Streamsets/Cask/NiFi built-in is a miss. These kinds of visual streaming connector tools make working with streams super productive and useful, as opposed to a developer only secret feature.