all the time. most of my quilts are 2 quilts in one...that way, if a person wants a change they can flip it over and have a new look...sometimes i use flannel on one side and regular cotton on the other...fall/winter and spring/summer.it is more fun than just a whole cloth backing...although every once in awhile i do one of those and it looks as good on the back once it's quilted...may as well be a whole new quilt ;)
the only problem? if hand quilting you wind up with lots of seams to work with...machine quilting it's not such an issue.