For us the ECS autoscaling feature is way too naive. We need to do our own controller on some more responsive metrics. The customization support is pretty bad.
One thing I'd like to see in the future is scaling actions that supported multipliers, as well as metric math support (scale service to request_count/acceptable_requests_per_service).
We settled on constant increases/decreases using queue depth thresholds but ideally ECS would support feeding multiple metrics and doing some basic math to figure out how much we're currently process, how long it would take to flush the queue, and how many more containers we need to drain in a timely fashion.
ECS is pretty dead simple (just run an agent on the host) and while it doesn't offer nearly the same feature set, it's really good operationally.
Some people here are tinkering with it for some non-core services.