getxb - 8:36 pm on Nov 8, 2010 (gmt 0)
Google doesn't care what utilities you use to test your site - they care about how fast the pages load for visitors.
Increasing page loading time = More visitor frustration = More bounces/exit rate = Less returning visitors = ... = Less credibility/brownie points for the website
So it will be interesting to learn HOW MUCH Google really cares.
It's interesting to note that the key figure in researching and building the YSlow tool is Steve Souders. He was then hired by Google and worked on Google's Page Speed tool.
@tedster: Thanks for the info!