Twitter has replaced Storm with Heron which provides up to 14 times more throughput and up to 10 times less latency on a word count topology, and helped them reduce the needed hardware to a third.
Hadoop is definitely the platform of choice for Big Data analysis and computation. While data Volume, Variety and Velocity increases, Hadoop as a batch processing framework cannot cope with the requirement for real time analytics. Spark, Storm and the Lambda Architecture can help bridge the gap between batch and event based processing.
Twitter has open-sourced Storm, its distributed, fault-tolerant, real-time computation system, at GitHub under the Eclipse Public License 1.0. Storm is the real-time processing system developed by BackType, which is now under the Twitter umbrella.