Ask HN: What are you using for scaling, monitoring and analytics?

With so many to choose from, what are you guys using and why? We are using AWS. This is what we are thinking of using...

Scalr.net - auto scaling for bringing up/down EC2 instances. Customizable, scripting and cheap. Not sure if proven though.

Cloudkick - monitoring. Easy UI and free.

Mixpanel - analytics. On action type analytics makes it easy to see which features are used and which are not.