I had tried earlier YSlow/Firebug combined with other tools (jslint,jsmin-packer) successfully. I was keen to find out what Page Speed has to offer. I was surprised at level of details and new features – page speed activity, a request overview and it also tells you the improvements of implementing the suggested changes.
I then tried Page speed.
Improvement needed on their own website.
Update (08 July 2009) – Myspace has released performance tracker tool for IE.