One of the talks I went to at Oracle Open World was one on measuring performance of your application on an Oracle database. The talk was by Cary Millsap of Method R titled "Instrumentation: Why You Should Care"
It was interesting in many ways, topics such as writing debug data to a ring bugger of shared memory reminded me of how we used to work before dtrace came a long.
There was one fantastic quote from Mr Millsap, which I think is worth repeating
"If obviously different experiences yield the same measurement, then clearly you're measuring the wrong thing"
Sage words indeed