It will definitely add a different flavor component to the brew. It may work well in a fruit beer (where the flavors could blend) or in a darker beer like a porter or stout (where the darker malts will help hide the cider). I would probably avoid using cider in a lighter-flavored beer,though, unless you want that flavor to be prominent.
"Give a man a beer, and he will waste an hour. Teach a man to brew, and he will waste a lifetime!" Bill Owen