API improvements, AWS SDK upgrades, etc.
Currently, the KinesisReceiver can loose some data in the case of certain failures (receiver and driver failures). Using the write ahead logs can mitigate some of the problem, but it is not ideal because WALs dont work with S3 (eventually consistency, etc.) which is the most likely file system to be used in the EC2 environment. Hence, we have to take a different approach to improving reliability for Kinesis. See https://issues.apache.org/jira/browse/SPARK-9215 for more details.