I have published an InfoQ news post about the AWS team's efforts to increase operational control over auto-scaled EC2 instances:
Amazon Web Services recently added several features to its Auto Scaling service to improve control over the managed Amazon EC2 instances. It is now possible to hook into the pending and terminating lifecycle state transitions to perform custom operations, which is also available for in service instances by means of a new standby state. The new DetachInstances API action now allows to remove instances from an Auto Scaling group.
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Continue reading the full post in AWS Adds Hooks Into Expanded Auto Scaling Lifecycle.