If the problem is not solved by using the default configuration & toolbars, then it is likely caused by shell extensions or similar 3rd party components, or by a particular file in your startup folder (which the empty folder test above should rule out). Crash, exit or high CPU when viewing certain directories has suggestions along that path.
I decided to uninstall -reinstall and the conclusion is that with the default configuration after installing DO it works fine, no slowness at all. But as soon as I load my previous configuration everything is slow (changing folders, opening menus, etc). is there any way to find out what slows down in the configuration? (tooobars?). Leo, Do you need anything that can help identify?
AFAIK one of the toolbars when loaded rendered DO immediatly slower. But I didn't pay attention to all of the involved links. I only remember the first two were menu buttons for favorites and recent.