Besides CCleaner Pro giving the handy Auto Updater -not having to go to the site to download and install the latest versions- to me what makes the big difference is that the Pro version now cleans automatically after you close your browser. (If you choose the option it do that.) This was a feature I had suggested to Piriform already quite some time ago. I used to have Window Washer from Webroot which also could be set to automatically clean the browser after closing: "Window Washer 2011" But with Windows 7 it did not work anymore -they discontinued support for it- and now it's bundled with Webroot's Security software: Since I don't use Webroot's security software I missed the automatic cleaning of the browser by Window Washer. That's when I suggested to Pirifom they implement this handy feature on CCleaner. They responded it was a good idea, and had put it on the "things to do" list. I'm glad to discovered they did implement it in the Professional version of CCleaner.