If you don't like how precisely you must mouse in Microsoft Word 2008 to delete comment balloons, note that you can Control-click (right-click) a balloon to pop up a contextual menu. From the menu choose Delete Comment, and you're done.
Also, to get rid of all comments at once, choose Tools > Customize Keyboard and set up a keyboard shortcut to go with the DeleteAllComments command, available in the Tools category. Oddly, there's no Delete Comment keyboard customization option that I can find.
From Tonya Engst