This has saved me so much time! If you need to put some text (or whatever) on a lot of pages, then after two weeks you change your mind.. Then it's boring changing the same text on every page, and probably you make some spelling mistakes, and then it's even more boring..
But with this plugin you can make a text in a widget, and then put the shortcode where you feel like.. Then all you have to do to change all the pages is to change the one widget.. 5 stars no doubt!
EDIT: This plugin goes great along with the WP Widget Cache plugin which allows you to controll what widget to cache and for how long you want to cache it. If you have anything heavy on your site, put it in a widget an cache it. In that way you'll speed up the site.