DataDog is an important part of monitoring at SmarterAgent, where we use their API's and Integrations heavily, especially the CloudWatch integrations for Amazon's Web Services (AWS). Using these, we have been able to put up effective dashboards for new environments in a matter of minutes.
We leverage DD’s API primarily for eventing. For example, deployments are posted to DataDog (as events), where they overlay our metrics. This has proven very useful in tracking changes due to deploys and/or configuration changes.
While we do leverage the DataDog agent for standard and custom metrics, DataDog’s ability to put together dashboards (and alerting) for AWS without any modifications to the host is what really closed the deal for us.