Google claims over 120,000 sites are currently using it to speed up their web sites.
Webmasters and server administrators can learn more about this server tool at developers.google.com/speed/pagespeed/mod.
As you know, Google finds page speed important. They use it as a factor in both organic and paid search. They have a page speed analytics tool in Webmaster Tools and several other tools to help webmaster measure their web page speed.