Load testing updates - Rob, I feel your pain
I just wanted to throw my two cents in on this subject of load testing updates to highly trafficed sites. http://weblogs.asp.net/rhoward/archive/2007/05/21/www-asp-net-update-part-2.aspx
Before a falling out with a customer over contractual issues, we developed code and managed their web servers. We were never able to fully test major changes under load. One update we had caused lingering problems, but it was what they wanted and stated they had to have. Interestingly, I feel that this update led to the contractual issues.
Rob, I feel your pain.