NewRelic is a suite of tools that provide you with the ability to see all aspects of your application. The integration with AWS was trivial and we had data to consume within minutes. Our favorite parts of the app:
APM -- We use this often to find hot spots in our application. We compare the before-and-after with software updates to make sure changes are operating as expected.
BROWSER -- Gives us great insight into how our application is performing on the desktop and what type of browsers are in use. When used with the APM, these two components give you the ability to really X-RAY your application.
SYNTHETICS -- We've built custom monitors using the scripting language and use this to verify everything is working as expected. We love the historical ability to see load time by location.
PLUGINS -- Easy way for us to load stats for our EC2, ELB, SNS, SQS, RDS instances.... all done via a simple plug-in. Now we have one place to look for everything.
INSIGHTS -- My favorite. Write custom queries using a built-in query language and save commonly used queries to dashboards. We display dashboard around the office to monitor all our NewRelic collected metrics in real-time. *Awesome*
Support -- not a component, but the NewRelic support team has always been responsive and helpful. Great to work with.