We have been using a Progressive Enhancement approach much more in relation to our web work. In a nutshell, this means we provide a good looking site on all browsers, then on more modern browsers, we use features that let us stay even closer to our designers' designs. So while we might not be able to show rounded corners to users of IE8, we can still provide meaningful content and a site that looks good and save the fancy features for browsers that do support them.
Another example of this is our Responsive Web Design projects. You may be familiar with the idea that, as you resize the browser, the design responds to the constraints given. However, IE8 doesn't support the all of the features that are needed for Reponsive Design, especially media queries. But that's OK, because most IE8 use is on the desktop, so we provide the core value—in this case, the desktop view—to IE8, and on more modern browsers, progressively enhance for the responsiveness.
Nerdy, relevant stuff as the number of browser versions continues to grow. And if none of this makes sense, this little cartoon poem may do the trick.