Over the past year, I moved a vbulletin site from an entry level dedicated server with no page speed optimizations in use, to an enterprise dedicated server with quad core processors and SSD drives, page speed optimizations, and use of a CDN, and Google's "Site Performance" tool shows no significant difference in the crappy page speed it says I have (slower than 70% of other websites)!
It still says my pages on average take 4.8 seconds to load, when most 3rd party tools I use average between 2-3 seconds, and browsing through the site - it is obviously faster than most sites I visit.
This is despite the fact that 3rd party page speed tools show a dramatic improvement in load time, and visitors to the site have told me it is faster as well.
Since one of the main reasons I started working on page speed was because it became an SEO ranking factor, I wonder if this broken "Site Performance" guage is what Google is using to determine that? If so, maybe they should fix it or use something else?
Does anyone have experience where this site performance tool actually seems to recognize changes you've made to your pages' load time?
I know a few other webmasters who have seen the same thing I am seeing.