enrise.com VS.

eschrade.com

Load Testing the Magento checkout is, in theory, difficult.  Well, not so much difficult as time consuming.  It is my personal opinion that most Magento load testing is done either poorly or incompletely.  Load testing read-only pages usually means hitting the same page over and over again.  This is counter productive because it allows the system to cache re-used data and skew load testing results to the positive.  I have yet to see a load test that yields performance results that matches production.