John Resig:

There are a number of techniques that the Dromaeo suite uses in order to achieve accurate results. Together they provide a solid foundation for allowing significant performance analysis to be completed.

Acidus:

The majority of widely known web performance optimization practices today focus on the application tier or the database tier. Traditional performance testings tools do no front end optimization testing. And yet the front end has the biggest impact on web application performance in modern applications. Do you see the disconnect yet?

This is an enormous opportunity.