Today I installed their standard Heroku add-on and, after only half a day of usage, I'm blown away. Here's what you get for free:
- App Response Time, Throughput & Breakdown by Component
- Real-User Response Time, Throughput & Breakdown by Layer
- Server Resource and Availability Monitoring
- App Availability Monitoring, Alerting, and Notification (bye, bye Pingdom)
- Error Detection, Alerting, & Analysis
- Awesome graphs
- Full list here.
The amount of information it can gather is impressive, and it can be installed on any platform, even mobile apps. I think it's worth checking it out.
Here is a pretty detailed review by net.tutsplus.
Oh, did I mention their support is awesome? I received replies in under an hour, four times in a row; for quite unimportant stuff too.