It depends on whether the topic is one that the child is using in the mean time.  For say, a language course where they don't study the language for a few years and then are thinking about taking the AP course, I'd consider it.  Same with a math course if they're not taking more math.  But if they are using the material that they learned in the college class, I would see taking the AP class as pointless, not rigorous.
I echo this question, too:
If the AP course is more rigorous than the college course, why is the student taking the college course?