When you move your cursor over the preview image it should turn to a +, just like CS3. A left mouse click will engage the loupe.
If it does not show go to general preferences and deselect Ctrl + Click opens Loupe.
Thanks Curt and Noel! I knew that it had to be simple. I, for some reason, did not read that menu item in the General pane in Preferences. The CTRL+click for Loupe was checked. If I had read that, I would have known....duh!