While running the Internet Explorer 9 beta for the first time, it might have provided with a window listing the add-on which are slowing down your browser performance, and allowing you to disable or remove it to speed up. Add-ons, such as toolbars, can enhance your browsing experience, but they can also slow it down. This is one of the problems browsers face and the user blames the browser for it while the real culprit is the add-on.
So when you add a new add-on, IE9 beta while starting will show the notification bar at the bottom of IE9 , click on disable addons… will provide the add-on advisor.
This advisor provides you with the loading time information and you can adjust the total add-on time and accordingly you can disable them to speed up your browser.
You can also run that Performance advisor manually, just right click on the empty space near the ‘New tab’ and tick the ‘command bar’ to show .
From the command bar , Tools > Toolbars > Disable add-ons.. will provide the performance advisor window. (thanks to @rkquotes for the tip)
This is one of the many cool features of IE9 beta. If you haven’t yet tried it get it from http://windows.microsoft.com/en-US/internet-explorer/download/ie-9/worldwide