With New Relics Real User Monitoring, Application Performance monitoring and ServerMonitoring, New Relic has you covered. Everything you need to know about your application is there. And if you deploy New Relic right now, you'll get a free copy of Eric Ries' "the Lean Startup".
Build-Measure-Learn is a key concept of the lean startup, and NewRelic makes that measuring easy
Get it today by going to New Relic dot com.