Plitvice is definitely worth the 11 hour drive to get there.  It took about 9 hours to comfortably see the park, and with no one there it was peaceful.  I took the time to read a bit, of course.  The park is very similar to Great Smoky Mountains National Park, rolling hills, deciduous trees, ice cold water.  The waterfalls seem endless.  The pictures all look the same, but walking for 9 hours and seeing different, complex waterfalls is amazing.  In the afternoon the sun came out and the colors followed.  The water, aquamarine; the clouds, white; the moss, green; the sky blue, and all pure colors. (photos, more)