As someone about to invest big time in spark streaming for processing event series data I'm wondering if you could comment on what makes it a bad for for your workload.
See other comment about Spark and frameworks. If you are just starting out with stream processing I would highly recommend using the best-of-breed frameworks. Frameworks provide abstractions that let you focus on solving your domain problems quickly, you don't want to have to worry about the plumbing until you've solved those.